In the immediate aftermath of the Second World War, Germany was split into four zones, each administered by France, the United Kingdom, the United States and the Soviet Union respectively. In 1949, the Soviet-controlled zone formed the German Democratic Republic (East Germany), while the rest became the Federal Republic of Germany (West Germany). In this time, Berlin was also split into four zones, and the three non-Soviet zones formed West Berlin, which was a part of West Germany (although the West's administrative capital was moved to Bonn). One population grows, while the other declines Between 1949 and 1961, an estimated 2.7 million people migrated from East to West Germany. East Germany had a communist government with a socialist economy and was a satellite state of the Soviet Union, whereas West Germany was a liberal democracy with a capitalist economy, and western autonomy increased over time. Because of this difference, West Germany was a much freer society with more economic opportunities. During the German partition, the population of the west grew, from 51 million in 1950 to 62.7 million in 1989, whereas the population of East Germany declined from 18.4 million to just 16.4 million during this time. Little change after reunification In 1989, after four decades of separation, the process of German reunification began. The legal and physical barriers that had split the country were removed, and Germans could freely travel within the entire country. Despite this development, population growth patterns did not change. The population of the 'new states' (East Germany) continued to decline, whereas the population of the west grew, particularly in the 1990s, the first decade after reunification. The reasons for this continued imbalance between German population in the east and west, is mostly due to a low birth rate and internal migration within Germany. Despite the fact that levels of income and unemployment in the new states have gotten closer to those reported for the west (a major obstacle after reunification), life and opportunities in the west continue to attract young Germans from rural areas in the east with detrimental effect on the economy and demography of the new states.

In 1800, the region of Germany was not a single, unified nation, but a collection of decentralized, independent states, bound together as part of the Holy Roman Empire. This empire was dissolved, however, in 1806, during the Revolutionary and Napoleonic eras in Europe, and the German Confederation was established in 1815. Napoleonic reforms led to the abolition of serfdom, extension of voting rights to property-owners, and an overall increase in living standards. The population grew throughout the remainder of the century, as improvements in sanitation and medicine (namely, mandatory vaccination policies) saw child mortality rates fall in later decades. As Germany industrialized and the economy grew, so too did the argument for nationhood; calls for pan-Germanism (the unification of all German-speaking lands) grew more popular among the lower classes in the mid-1800s, especially following the revolutions of 1948-49. In contrast, industrialization and poor harvests also saw high unemployment in rural regions, which led to waves of mass migration, particularly to the U.S.. In 1886, the Austro-Prussian War united northern Germany under a new Confederation, while the remaining German states (excluding Austria and Switzerland) joined following the Franco-Prussian War in 1871; this established the German Empire, under the Prussian leadership of Emperor Wilhelm I and Chancellor Otto von Bismarck. 1871 to 1945 - Unification to the Second World War The first decades of unification saw Germany rise to become one of Europe's strongest and most advanced nations, and challenge other world powers on an international scale, establishing colonies in Africa and the Pacific. These endeavors were cut short, however, when the Austro-Hungarian heir apparent was assassinated in Sarajevo; Germany promised a "blank check" of support for Austria's retaliation, who subsequently declared war on Serbia and set the First World War in motion. Viewed as the strongest of the Central Powers, Germany mobilized over 11 million men throughout the war, and its army fought in all theaters. As the war progressed, both the military and civilian populations grew increasingly weakened due to malnutrition, as Germany's resources became stretched. By the war's end in 1918, Germany suffered over 2 million civilian and military deaths due to conflict, and several hundred thousand more during the accompanying influenza pandemic. Mass displacement and the restructuring of Europe's borders through the Treaty of Versailles saw the population drop by several million more.

Reparations and economic mismanagement also financially crippled Germany and led to bitter indignation among many Germans in the interwar period; something that was exploited by Adolf Hitler on his rise to power. Reckless printing of money caused hyperinflation in 1923, when the currency became so worthless that basic items were priced at trillions of Marks; the introduction of the Rentenmark then stabilized the economy before the Great Depression of 1929 sent it back into dramatic decline. When Hitler became Chancellor of Germany in 1933, the Nazi government disregarded the Treaty of Versailles' restrictions and Germany rose once more to become an emerging superpower. Hitler's desire for territorial expansion into eastern Europe and the creation of an ethnically-homogenous German empire then led to the invasion of Poland in 1939, which is considered the beginning of the Second World War in Europe. Again, almost every aspect of German life contributed to the war effort, and more than 13 million men were mobilized. After six years of war, and over seven million German deaths, the Axis powers were defeated and Germany was divided into four zones administered by France, the Soviet Union, the UK, and the U.S.. Mass displacement, shifting borders, and the relocation of peoples based on ethnicity also greatly affected the population during this time. 1945 to 2020 - Partition and Reunification In the late 1940s, cold war tensions led to two distinct states emerging in Germany; the Soviet-controlled east became the communist German Democratic Republic (DDR), and the three western zones merged to form the democratic Federal Republic of Germany. Additionally, Berlin was split in a similar fashion, although its location deep inside DDR territory created series of problems and opportunities for the those on either side. Life quickly changed depending on which side of the border one lived. Within a decade, rapid economic recovery saw West Germany become western Europe's strongest economy and a key international player. In the east, living standards were much lower, although unemployment was almost non-existent; internationally, East Germany was the strongest economy in the Eastern Bloc (after the USSR), though it eventually fell behind the West by the 1970s. The restriction of movement between the two states also led to labor shortages in t...

1941 marked an escalation of the Second World War in Europe. By the middle of the year, Germany and its European allies had already consolidated power across most of the continent, with only the United Kingdom and Soviet Union not under Axis control or on neutral terms with Germany. As population sizes were fundamental to the war effort, both in terms of military manpower and the workforce of the home front, the annexation of other countries proved vital in supplying new volunteers, conscripts, and forced laborers for the Axis war effort. Together, Germany and Austria had a similar population to the rest of Europe's Axis powers combined, with all giving a total population of 154 million. However, the total population of the Axis-occupied territories in Europe was comparable to the Axis home fronts themselves, at almost 130 million people

Germans in the East Eastern Europe had a sizeable population of ethnic Germans who often worked with the Axis powers, and the German Army recruited upwards of a million volunteers from occupied countries. The Soviet Union in particular had a number of Russia German enclaves across the region, that reached as far as the Volga river and Kazakhstan and numbered at several million people. In Russia, these communities had existed for centuries, but they were ostracized or mistrusted by Soviet leadership and the deaths of these communities under Stalin's regime is often considered genocide. In addition to ethnic Germans, collaborators also included large numbers of Eastern Europeans who sympathized with Nazi ideology, or were hostile to Soviet or communist expansion; this also included ethnic minorities, such as Muslims from the Balkans or USSR.

Collaborators in the West The perceived threat of communism in the west saw men volunteer from countries such as France, the Netherlands, or Norway, to fight in the Axis armies. The fluctuating borders of the interwar period also meant that there were many German communities across the borders of neighboring countries, whose men also enlisted in the Wehrmacht. Within these occupied countries, conspirators with local knowledge were used to track down Jews and political adversaries, and many collaborated in order to elevate their positions in the government or enterprises. Apart from Austria, however, the majority of the public in annexed territories were unsupportive or hostile to their occupiers, and after the war, many of the surviving collaborators were tried (and often executed) for their actions.

In 1938, the year before the outbreak of the Second world War, the countries with the largest populations were China, the Soviet Union, and the United States, although the United Kingdom had the largest overall population when it's colonies, dominions, and metropole are combined. Alongside France, these were the five Allied "Great Powers" that emerged victorious from the Second World War. The Axis Powers in the war were led by Germany and Japan in their respective theaters, and their smaller populations were decisive factors in their defeat. Manpower as a resource In the context of the Second World War, a country or territory's population played a vital role in its ability to wage war on such a large scale. Not only were armies able to call upon their people to fight in the war and replenish their forces, but war economies were also dependent on their workforce being able to meet the agricultural, manufacturing, and logistical demands of the war. For the Axis powers, invasions and the annexation of territories were often motivated by the fact that it granted access to valuable resources that would further their own war effort - millions of people living in occupied territories were then forced to gather these resources, or forcibly transported to work in manufacturing in other Axis territories. Similarly, colonial powers were able to use resources taken from their territories to supply their armies, however this often had devastating consequences for the regions from which food was redirected, contributing to numerous food shortages and famines across Africa, Asia, and Europe. Men from annexed or colonized territories were also used in the armies of the war's Great Powers, and in the Axis armies especially. This meant that soldiers often fought alongside their former-enemies. Aftermath The Second World War was the costliest in human history, resulting in the deaths of between 70 and 85 million people. Due to the turmoil and destruction of the war, accurate records for death tolls generally do not exist, therefore pre-war populations (in combination with other statistics), are used to estimate death tolls. The Soviet Union is believed to have lost the largest amount of people during the war, suffering approximately 24 million fatalities by 1945, followed by China at around 20 million people. The Soviet death toll is equal to approximately 14 percent of its pre-war population - the countries with the highest relative death tolls in the war are found in Eastern Europe, due to the intensity of the conflict and the systematic genocide committed in the region during the war.

Sources: Publications of the Federal Statistical Office, scientific publications

Over the course of the Second World War, approximately 44.5 percent of the Soviet population and 8.7 of Soviet territory was occupied by the Axis forces at some point. Despite being allied in the war's early stages, with both countries invading Poland in 1939 via the Molotov-Ribbentrop Pact, Germany would launch Operation Barbarossa, the invasion of the USSR, in 1941, which would become the largest military invasion in history. Movement of the Eastern Front The surprise invasion began on June 22, and Axis forces caught the Soviets off-guard, quickly pushing their way eastward along a frontline that stretched from the Baltic to Black seas. The length of the front-line allowed Axis forces to execute pincer movements around cities and strongholds, which cut off large numbers of Soviet soldiers from their supply lines, as well as preventing reinforcements; in this process millions of Soviet troops were taken as prisoner. Within three weeks, the Germans had taken much of present-day Poland, Belarus, and the Baltic states, before taking Moldova and Ukraine in September, and pushing into western Russia between September and December. The front lines had reached the outskirts of Moscow by November, before exhaustion and cold weather helped Soviet forces hold the line and stall the German offensive. The Red Army was then able to regroup and turning the Germans' own tactics against them, using two-pronged attacks to encircle large numbers of troops, although harsh weather made this stage of the conflict much slower.

The lines remained fairly static until mid-1942, when the Germans focused their offensive on the south, concentrating on the Caucasian oil fields and the Volga River. By November 1942, Axis forces had pushed into these regions, establishing what would ultimately be the largest amount of occupied Soviet territory during the war. Once again, winter halted the Axis advance, and allowed the Red Army to regroup. Learning from the previous year, the Axis command strengthened their forces near Moscow in anticipation of the Soviet counter-offensive, but were caught off-guard by a second counter-offensive in the south, most famously at Stalingrad. The Battle of Stalingrad would come to epitomize the extreme loss, destruction, and brutality of war on the eastern front, with conflict continuing in the city months after the rest of the Axis forces had been pushed west. As 1943 progressed, the Red Army gained momentum by targeting inferiorly-trained and equipped non-German regiments. The spring then became something of a balancing act for the Axis powers, as the Soviets consistently attacked weak points, and German regiments were transferred to reinforce these areas. In the summer of 1943, the front line was static once more, however the momentum was with the Soviets, who were able to capitalize on victories such as Kursk and gradually force the Axis powers back. By 1944, the Red Army had re-captured much of Ukraine, and had re-taken the south by the summer. When the Western Allies arrived in France in June, the Soviets were already pushing through Ukraine and Belarus, towards Berlin. In August 1944, the last Axis forces were pushed out of Soviet territory, and Soviet forces continued their push towards the German capital, which fell in May 1945. Soviet death toll In addition to the near-five million Soviet troops who died during Operation Barbarossa, millions of civilians died through starvation, areal bombardment, forced labor, and systematic murder campaigns. Due to the nature and severity of Soviet losses, total figures are difficult to estimate; totals of 15-20 million civilians and 7-9 million military deaths are most common. Further estimates suggest that the disruption to fertility, in addition to the high death toll, meant that the USSR's population in 1946 was 40 million lower than it would have been had there been no war.

The Holocaust was the systematic extermination of Europe's Jewish population in the Second World War, during which time, up to six million Jews were murdered as part of Nazi Germany's "Final Solution to the Jewish Question". In the context of the Second World War, the term "Holocaust" is traditionally used to reference the genocide of Europe's Jews, although this coincided with the Nazi regime's genocide and ethnic cleansing of an additional eleven million people deemed "undesirable" due to their ethnicity, beliefs, disability or sexuality (among others). During the Holocaust, Poland's Jewish population suffered the largest number of fatalities, with approximately three million deaths. Additionally, at least one million Jews were murdered in the Soviet Union, while Hungary, Latvia, Lithuania, the Netherlands and Yugoslavia also lost the majority of their respective pre-war Jewish populations. The Holocaust in Poland In the interwar period, Europe's Jewish population was concentrated in the east, with roughly one third living in Poland; this can be traced back to the Middle Ages, when thousands of Jews flocked to Eastern Europe to escape persecution. At the outbreak of the Second World War, it is estimated that there were 3.4 million Jews living in Poland, which was approximately ten percent of the total population. Following the German invasion of Poland, Nazi authorities then segregated Jews in ghettos across most large towns and cities, and expanded their network of concentration camps throughout the country. In the ghettos, civilians were deprived of food, and hundreds of thousands died due to disease and starvation; while prison labor was implemented under extreme conditions in concentration camps to fuel the German war effort. In Poland, six extermination camps were also operational between December 1941 and January 1945, which saw the mass extermination of approximately 2.7 million people over the next three years (including many non-Poles, imported from other regions of Europe). While concentration camps housed prisoners of all backgrounds, extermination camps were purpose-built for the elimination of the Jewish race, and over 90% of their victims were Jewish. The majority of the victims in these extermination camps were executed by poison gas, although disease, starvation and overworking were also common causes of death. In addition to the camps and ghettos, SS death squads (Einsatzgruppen) and local collaborators also committed widespread atrocities across Eastern Europe. While the majority of these atrocities took place in the Balkan, Baltic and Soviet regions, they were still prevalent in Poland (particularly during the liquidation of the ghettos), and the Einsatzgruppen alone are estimated to have killed up to 1.3 million Jews throughout the Holocaust. By early 1945, Soviet forces had largely expelled the German armies from Poland and liberated the concentration and extermination camps; by this time, Poland had lost roughly ninety percent of its pre-war Jewish population, and suffered approximately three million further civilian and military deaths. By 1991, Poland's Jewish population was estimated to be just 15 thousand people, while there were fewer than two thousand Jews recorded as living in Poland in 2018.

Most estimates place the total number of deaths during the Second World War at around 70-85 million people. Approximately 17 million of these deaths (20-25 percent of the total) were due to crimes against humanity carried out by the Nazi regime in Europe. In comparison to the millions of deaths that took place through conflict, famine, or disease, these 17 million stand out due to the reasoning behind them, along with the systematic nature and scale in which they were carried out. Nazi ideology claimed that the Aryan race (a non-existent ethnic group referring to northern Europeans) was superior to all other ethnicities; this became the justification for German expansion and the extermination of others. During the war, millions of people deemed to be of lesser races were captured and used as slave laborers, with a large share dying of exhaustion, starvation, or individual execution. Murder campaigns were also used for systematic extermination; the most famous of these were the extermination camps, such as at Auschwitz, where roughly 80 percent of the 1.1 million victims were murdered in gas chambers upon arrival at the camp. German death squads in Eastern Europe carried out widespread mass shootings, and up to two million people were killed in this way. In Germany itself, many disabled, homosexual, and "undesirables" were also killed or euthanized as part of a wider eugenics program, which aimed to "purify" German society.

The Holocaust Of all races, the Nazi's viewed Jews as being the most inferior. Conspiracy theories involving Jews go back for centuries in Europe, and they have been repeatedly marginalized throughout history. German fascists used the Jews as scapegoats for the economic struggles during the interwar period. Following Hitler's ascendency to the Chancellorship in 1933, the German authorities began constructing concentration camps for political opponents and so-called undesirables, but the share of Jews being transported to these camps gradually increased in the following years, particularly after Kristallnacht (the Night of Broken Glass) in 1938. In 1939, Germany then invaded Poland, home to Europe's largest Jewish population. German authorities segregated the Jewish population into ghettos, and constructed thousands more concentration and detention camps across Eastern Europe, to which millions of Jews were transported from other territories. By the end of the war, over two thirds of Europe's Jewish population had been killed, and this share is higher still when one excludes the neutral or non-annexed territories.

Lebensraum Another key aspect of Nazi ideology was that of the Lebensraum (living space). Both the populations of the Soviet Union and United States were heavily concentrated in one side of the country, with vast territories extending to the east and west, respectively. Germany was much smaller and more densely populated, therefore Hitler aspired to extend Germany's territory to the east and create new "living space" for Germany's population and industry to grow. While Hitler may have envied the U.S. in this regard, the USSR was seen as undeserving; Slavs were the largest major group in the east and the Nazis viewed them as inferior, which was again used to justify the annexation of their land and subjugation of their people. As the Germans took Slavic lands in Poland, the USSR, and Yugoslavia, ethnic cleansings (often with the help of local conspirators) became commonplace in the annexed territories. It is also believed that the majority of Soviet prisoners of war (PoWs) died through starvation and disease, and they were not given the same treatment as PoWs on the western front. The Soviet Union lost as many as 27 million people during the war, and 10 million of these were due to Nazi genocide. It is estimated that Poland lost up to six million people, and almost all of these were through genocide.

Throughout the 19th century, what we know today as Poland was not a united, independent country; apart from a brief period during the Napoleonic Wars, Polish land was split between the Austro-Hungarian, Prussian (later German) and Russian empires. During the 1800s, the population of Poland grew steadily, from approximately nine million people in 1800 to almost 25 million in 1900; throughout this time, the Polish people and their culture were oppressed by their respective rulers, and cultural suppression intensified following a number of uprisings in the various territories. Following the outbreak of the First World War, it is estimated that almost 3.4 million men from Poland served in the Austro-Hungarian, German and Russian armies, with a further 300,000 drafted for forced labor by the German authorities. Several hundred thousand were forcibly resettled in the region during the course of the war, as Poland was one of the most active areas of the conflict. For these reasons, among others, it is difficult to assess the extent of Poland's military and civilian fatalities during the war, with most reliable estimates somewhere between 640,000 and 1.1 million deaths. In the context of present-day Poland, it is estimated that the population fell by two million people in the 1910s, although some of this was also due to the Spanish Flu pandemic that followed in the wake of the war.

Poland 1918-1945

After more than a century of foreign rule, an independent Polish state was established by the Allied Powers in 1918, although it's borders were considerably different to today's, and were extended by a number of additional conflicts. The most significant of these border conflicts was the Polish-Soviet War in 1919-1920, which saw well over 100,000 deaths, and victory helped Poland to emerge as the Soviet Union's largest political and military rival in Eastern Europe during the inter-war period. Economically, Poland struggled to compete with Europe's other powers during this time, due to its lack of industrialization and infrastructure, and the global Great Depression of the 1930s exacerbated this further. Political corruption and instability was also rife in these two decades, and Poland's leadership failed to prepare the nation for the Second World War. Poland had prioritized its eastern defenses, and some had assumed that Germany's Nazi regime would see Poland as an ally due to their shared rivalry with the Soviet Union, but this was not the case. Germany invaded Poland on September 1, 1939, in the first act of the War, and the Soviet Union launched a counter invasion on September 17; Germany and the Soviet Union had secretly agreed to do this with the Molotov-Ribbentrop Pact in August, and had succeeded in taking the country by September's end. When Germany launched its invasion of the Soviet Union in 1941 it took complete control of Poland, which continued to be the staging ground for much of the fighting between these nations. It has proven difficult to calculate the total number of Polish fatalities during the war, for a variety of reasons, however most historians have come to believe that the figure is around six million fatalities, which equated to almost one fifth of the entire pre-war population; the total population dropped by four million throughout the 1940s. The majority of these deaths took place during the Holocaust, which saw the Nazi regime commit an ethnic genocide of up to three million Polish Jews, and as many as 2.8 million non-Jewish Poles; these figures do not include the large number of victims from other countries who died after being forcefully relocated to concentration camps in Poland.

Post-war Poland

The immediate aftermath of the war was also extremely unorganized and chaotic, as millions were forcefully relocated from or to the region, in an attempt to create an ethnically homogenized state, and thousands were executed during this process. A communist government was quickly established by the Soviet Union, and socialist social and economic policies were gradually implemented over the next decade, as well as the rebuilding, modernization and education of the country. In the next few decades, particularly in the 1980s, the Catholic Church, student groups and trade unions (as part of the Solidarity movement) gradually began to challenge the government, weakening the communist party's control over the nation (although it did impose martial law and imprison political opponent throughout the early-1980s). Increasing civil unrest and the weakening of Soviet influence saw communism in Poland come to an end in the elections of 1989. Throughout the 1990s, Poland's population growth stagnated at around 38.5 million people, before gradually decreasing since the turn of the millennium, to 37.8 million people in 2020. This decline was mostly due to a negative migration rate, as Polish workers could now travel more freely to Western Europea...

The fertility rate of a country is the average number of children that women from that country will have throughout their reproductive years. In Germany in 1800, the average woman of childbearing age would have 5.4 children over the course of their lifetime. It remained around this number until the late 1820s, when it then dropped to just under five, which was a long-term effect of the Napoleonic Period in Europe. From this point until the end of the nineteenth century, Germany's fertility rate was rather sporadic, reaching it's lowest point in 1855 with an average of 4.6 births per woman, and it's highest point in 1875 (just after the foundation of the German Empire in 1871), with an average of 5.4 live births per woman. From the beginning of the twentieth century until the end of the Second World War, Germany's fertility rate dropped from around 5 children per woman in 1900, to 1.9 in 1945. The only time where the fertility rate increased was in the inter-war years. Like other countries heavily involved in the Second World War, Germany (both East and West) experienced a Baby Boom from the late 1940s to the late 1960s, however it then dropped to it's lowest point of just 1.3 children per woman by 1995, shortly after the re-unification of Germany. In recent years, Germany's fertility rate has gradually been increasing again, and is expected to reach 1.6 in 2020, its highest rate in over forty years.

For most of the Second World War, the Soviet Union had the largest number of active military personnel each year, peaking at over 12 million people in the war's final years. The Soviet Union's ability to draw from its larger population was decisive in its eventual victory over Germany in 1945, whose eastern forces were greatly diminished by 1944 after it had already suffered heavy losses fighting the Soviets and was then forced to fight on the western front.

Each of the Great Powers had varying conscription systems in place that allowed them to draft citizens into the military. In the U.S., over 50 million men aged 18-45 would register for the draft before the war's end, and over 10 million of these were inducted into the military (alongside volunteers and those already in service). Conscription in Japan grew more aggressive as the war progressed, and its armed forces doubled in size in the final two years of the war.

Estimates for the total death count of the Second World War generally range somewhere between 70 and 85 million people. The Soviet Union suffered the highest number of fatalities of any single nation, with estimates mostly falling between 22 and 27 million deaths. China then suffered the second greatest, at around 20 million, although these figures are less certain and often overlap with the Chinese Civil War. Over 80 percent of all deaths were of those from Allied countries, and the majority of these were civilians. In contrast, 15 to 20 percent were among the Axis powers, and the majority of these were military deaths, as shown in the death ratios of Germany and Japan. Civilian deaths and atrocities It is believed that 60 to 67 percent of all deaths were civilian fatalities, largely resulting from war-related famine or disease, and war crimes or atrocities. Systematic genocide, extermination campaigns, and forced labor, particularly by the Germans, Japanese, and Soviets, led to the deaths of millions. In this regard, Nazi activities alone resulted in 17 million deaths, including six million Jews in what is now known as The Holocaust. Not only was the scale of the conflict larger than any that had come before, but the nature of and reasoning behind this loss make the Second World War stand out as one of the most devastating and cruelest conflicts in history. Problems with these statistics Although the war is considered by many to be the defining event of the 20th century, exact figures for death tolls have proven impossible to determine, for a variety of reasons. Countries such as the U.S. have fairly consistent estimates due to preserved military records and comparatively few civilian casualties, although figures still vary by source. For most of Europe, records are less accurate. Border fluctuations and the upheaval of the interwar period mean that pre-war records were already poor or non-existent for many regions. The rapid and chaotic nature of the war then meant that deaths could not be accurately recorded at the time, and mass displacement or forced relocation resulted in the deaths of many civilians outside of their homeland, which makes country-specific figures more difficult to find. Early estimates of the war’s fatalities were also taken at face value and formed the basis of many historical works; these were often very inaccurate, but the validity of the source means that the figures continue to be cited today, despite contrary evidence.

In comparison to Europe, estimate ranges are often greater across Asia, where populations were larger but pre-war data was in short supply. Many of the Asian countries with high death tolls were European colonies, and the actions of authorities in the metropoles, such as the diversion of resources from Asia to Europe, led to millions of deaths through famine and disease. Additionally, over one million African soldiers were drafted into Europe’s armies during the war, yet individual statistics are unavailable for most of these colonies or successor states (notably Algeria and Libya). Thousands of Asian and African military deaths went unrecorded or are included with European or Japanese figures, and there are no reliable figures for deaths of millions from countries across North Africa or East Asia. Additionally, many concentration camp records were destroyed, and such records in Africa and Asia were even sparser than in Europe. While the Second World War is one of the most studied academic topics of the past century, it is unlikely that we will ever have a clear number for the lives lost in the conflict.

In the past four centuries, the population of the United States has grown from a recorded 350 people around the Jamestown colony of Virginia in 1610, to an estimated 331 million people in 2020. The pre-colonization populations of the indigenous peoples of the Americas have proven difficult for historians to estimate, as their numbers decreased rapidly following the introduction of European diseases (namely smallpox, plague and influenza). Native Americans were also omitted from most censuses conducted before the twentieth century, therefore the actual population of what we now know as the United States would have been much higher than the official census data from before 1800, but it is unclear by how much. Population growth in the colonies throughout the eighteenth century has primarily been attributed to migration from the British Isles and the Transatlantic slave trade; however it is also difficult to assert the ethnic-makeup of the population in these years as accurate migration records were not kept until after the 1820s, at which point the importation of slaves had also been illegalized. Nineteenth century In the year 1800, it is estimated that the population across the present-day United States was around six million people, with the population in the 16 admitted states numbering at 5.3 million. Migration to the United States began to happen on a large scale in the mid-nineteenth century, with the first major waves coming from Ireland, Britain and Germany. In some aspects, this wave of mass migration balanced out the demographic impacts of the American Civil War, which was the deadliest war in U.S. history with approximately 620 thousand fatalities between 1861 and 1865. The civil war also resulted in the emancipation of around four million slaves across the south; many of whose ancestors would take part in the Great Northern Migration in the early 1900s, which saw around six million black Americans migrate away from the south in one of the largest demographic shifts in U.S. history. By the end of the nineteenth century, improvements in transport technology and increasing economic opportunities saw migration to the United States increase further, particularly from southern and Eastern Europe, and in the first decade of the 1900s the number of migrants to the U.S. exceeded one million people in some years. Twentieth and twenty-first century The U.S. population has grown steadily throughout the past 120 years, reaching one hundred million in the 1910s, two hundred million in the 1960s, and three hundred million in 2007. In the past century, the U.S. established itself as a global superpower, with the world's largest economy (by nominal GDP) and most powerful military. Involvement in foreign wars has resulted in over 620,000 further U.S. fatalities since the Civil War, and migration fell drastically during the World Wars and Great Depression; however the population continuously grew in these years as the total fertility rate remained above two births per woman, and life expectancy increased (except during the Spanish Flu pandemic of 1918).

Since the Second World War, Latin America has replaced Europe as the most common point of origin for migrants, with Hispanic populations growing rapidly across the south and border states. Because of this, the proportion of non-Hispanic whites, which has been the most dominant ethnicity in the U.S. since records began, has dropped more rapidly in recent decades. Ethnic minorities also have a much higher birth rate than non-Hispanic whites, further contributing to this decline, and the share of non-Hispanic whites is expected to fall below fifty percent of the U.S. population by the mid-2000s. In 2020, the United States has the third-largest population in the world (after China and India), and the population is expected to reach four hundred million in the 2050s.

In 1800, the population of the region now known as Tanzania was just over three million people. Throughout the 19th century, both as a collection of small kingdoms and later as a German colony (1897), Tanzania would see modest growth in its population, growing from three million at the start of the century to approximately four million by 1900. Following the handover of the region (then known as German East Africa) to the United Kingdom in 1919, the region would begin to see first a noticeable, and later an exponential increase in its population, rising to just under 8 million by 1950, and 33.5 million by the century’s end. This growth would slow somewhat beginning in the late 1980s to 1990s, in part the result of a rapid spread of the HIV/AIDS epidemic throughout the country. By 2020, Tanzania will have a population just under 60 million.