Over the past 160 years, life expectancy (from birth) in the United States has risen from 39.4 years in 1860, to 78.9 years in 2020. One of the major reasons for the overall increase of life expectancy in the last two centuries is the fact that the infant and child mortality rates have decreased by so much during this time. Medical advancements, fewer wars and improved living standards also mean that people are living longer than they did in previous centuries.

Despite this overall increase, the life expectancy dropped three times since 1860; from 1865 to 1870 during the American Civil War, from 1915 to 1920 during the First World War and following Spanish Flu epidemic, and it has dropped again between 2015 and now. The reason for the most recent drop in life expectancy is not a result of any specific event, but has been attributed to negative societal trends, such as unbalanced diets and sedentary lifestyles, high medical costs, and increasing rates of suicide and drug use.

A global phenomenon, known as the demographic transition, has seen life expectancy from birth increase rapidly over the past two centuries. In pre-industrial societies, the average life expectancy was around 24 years, and it is believed that this was the case throughout most of history, and in all regions. The demographic transition then began in the industrial societies of Europe, North America, and the West Pacific around the turn of the 19th century, and life expectancy rose accordingly. Latin America was the next region to follow, before Africa and most Asian populations saw their life expectancy rise throughout the 20th century.

For most of the world, throughout most of human history, the average life expectancy from birth was around 24. This figure fluctuated greatly depending on the time or region, and was higher than 24 in most individual years, but factors such as pandemics, famines, and conflicts caused regular spikes in mortality and reduced life expectancy. Child mortality The most significant difference between historical mortality rates and modern figures is that child and infant mortality was so high in pre-industrial times; before the introduction of vaccination, water treatment, and other medical knowledge or technologies, women would have around seven children throughout their lifetime, but around half of these would not make it to adulthood. Accurate, historical figures for infant mortality are difficult to ascertain, as it was so prevalent, it took place in the home, and was rarely recorded in censuses; however, figures from this source suggest that the rate was around 300 deaths per 1,000 live births in some years, meaning that almost one in three infants did not make it to their first birthday in certain periods. For those who survived to adolescence, they could expect to live into their forties or fifties on average. Modern figures It was not until the eradication of plague and improvements in housing and infrastructure in recent centuries where life expectancy began to rise in some parts of Europe, before industrialization and medical advances led to the onset of the demographic transition across the world. Today, global life expectancy from birth is roughly three times higher than in pre-industrial times, at almost 73 years. It is higher still in more demographically and economically developed countries; life expectancy is over 82 years in the three European countries shown, and over 84 in Japan. For the least developed countries, mostly found in Sub-Saharan Africa, life expectancy from birth can be as low as 53 years.

Throughout most of history, average life expectancy from birth was fairly consistent across the globe, at around 24 years. A major contributor to this was high rates of infant and child mortality; those who survived into adulthood could expect to live to their 50s or 60s, yet pandemics, food instability, and conflict did cause regular spikes in mortality across the entire population. Gradually, from the 16th to 19th centuries, there was some growth in more developed societies, due to improvements in agriculture, infrastructure, and medical knowledge. However, the most significant change came with the introduction of vaccination and other medical advances in the 1800s, which saw a sharp decline in child mortality and the onset of the demographic transition. This phenomenon began in more developed countries in the 1800s, before spreading to Latin America, Asia, and (later) Africa in the 1900s. As the majority of the world's population lives in countries considered to be "less developed", this figure is much closer to the global average. However, today, there is a considerable difference in life expectancies across these countries, ranging from 84.7 years in Japan to 53 years in the Central African Republic.

Life expectancy in India was 25.4 in the year 1800, and over the course of the next 220 years, it has increased to almost 70. Between 1800 and 1920, life expectancy in India remained in the mid to low twenties, with the largest declines coming in the 1870s and 1910s; this was because of the Great Famine of 1876-1878, and the Spanish Flu Pandemic of 1918-1919, both of which were responsible for the deaths of up to six and seventeen million Indians respectively; as well as the presence of other endemic diseases in the region, such as smallpox. From 1920 onwards, India's life expectancy has consistently increased, but it is still below the global average.

Life expectancy in Canada was just below forty in the year 1800, and over the course of the next 220 years, it is expected to have increased by more than double to 82.2 by the year 2020. Throughout this time, life expectancy in Canada progressed at a steady rate, with the most noticeable changes coming during the interwar period, where the rate of increase was affected by the Spanish Flu epidemic and both World Wars.

The child mortality rate in the United States, for children under the age of five, was 462.9 deaths per thousand births in 1800. This means that for every thousand babies born in 1800, over 46 percent did not make it to their fifth birthday. Over the course of the next 220 years, this number has dropped drastically, and the rate has dropped to its lowest point ever in 2020 where it is just seven deaths per thousand births. Although the child mortality rate has decreased greatly over this 220 year period, there were two occasions where it increased; in the 1870s, as a result of the fourth cholera pandemic, smallpox outbreaks, and yellow fever, and in the late 1910s, due to the Spanish Flu pandemic.

Life expectancy in China was just 32 in the year 1850, and over the course of the next 170 years, it is expected to more than double to 76.6 years in 2020. Between 1850 and 1950, finding reliable data proved difficult for anthropologists, however some events, such as the Taiping Rebellion and Dungan Revolt in the nineteenth century did reduce life expectancy by a few years, and also the Chinese Civil War and Second World War in the first half of the twentieth century. In the second half of the 1900s, Chinese life expectancy increased greatly, as the country became more industrialized and the standard of living increased.

Global life expectancy at birth has risen significantly since the mid-1900s, from roughly 46 years in 1950 to 73.2 years in 2023. Post-COVID-19 projections There was a drop of 1.7 years during the COVID-19 pandemic, between 2019 and 2021, however, figures resumed upon their previous trajectory the following year due to the implementation of vaccination campaigns and the lower severity of later strains of the virus. By the end of the century it is believed that global life expectancy from birth will reach 82 years, although growth will slow in the coming decades as many of the more-populous Asian countries reach demographic maturity. However, there is still expected to be a wide gap between various regions at the end of the 2100s, with the Europe and North America expected to have life expectancies around 90 years, whereas Sub-Saharan Africa is predicted to be in the low-70s. The Great Leap Forward While a decrease of one year during the COVID-19 pandemic may appear insignificant, this is the largest decline in life expectancy since the "Great Leap Forward" in China in 1958, which caused global life expectancy to fall by almost four years between by 1960. The "Great Leap Forward" was a series of modernizing reforms, which sought to rapidly transition China's agrarian economy into an industrial economy, but mismanagement led to tens of millions of deaths through famine and disease.

Life expectancy in the United Kingdom was below 39 years in the year 1765, and over the course of the next two and a half centuries, it is expected to have increased by more than double, to 81.1 by the year 2020. Although life expectancy has generally increased throughout the UK's history, there were several times where the rate deviated from its previous trajectory. These changes were the result of smallpox epidemics in the late eighteenth and early nineteenth centuries, new sanitary and medical advancements throughout time (such as compulsory vaccination), and the First world War and Spanish Flu epidemic in the 1910s.

It is only in the past two centuries where demographics and the development of human populations has emerged as a subject in its own right, as industrialization and improvements in medicine gave way to exponential growth of the world's population. There are very few known demographic studies conducted before the 1800s, which means that modern scholars have had to use a variety of documents from centuries gone by, along with archeological and anthropological studies, to try and gain a better understanding of the world's demographic development. Genealogical records One such method is the study of genealogical records from the past; luckily, there are many genealogies relating to European families that date back as far as medieval times. Unfortunately, however, all of these studies relate to families in the upper and elite classes; this is not entirely representative of the overall population as these families had a much higher standard of living and were less susceptible to famine or malnutrition than the average person (although elites were more likely to die during times of war). Nonetheless, there is much to be learned from this data. Impact of the Black Death In the centuries between 1200 and 1745, English male aristocrats who made it to their 21st birthday were generally expected to live to an age between 62 and 72 years old. The only century where life expectancy among this group was much lower was in the 1300s, where the Black Death caused life expectancy among adult English noblemen to drop to just 45 years. Experts assume that the pre-plague population of England was somewhere between four and seven million people in the thirteenth century, and just two million in the fourteenth century, meaning that Britain lost at least half of its population due to the plague. Although the plague only peaked in England for approximately eighteen months, between 1348 and 1350, it devastated the entire population, and further outbreaks in the following decades caused life expectancy in the decade to drop further. The bubonic plague did return to England sporadically until the mid-seventeenth century, although life expectancy among English male aristocrats rose again in the centuries following the worst outbreak, and even peaked at more than 71 years in the first half of the sixteenth century.

At the beginning of the 1840s, life expectancy from birth in Ireland was just over 38 years. However, this figure would see a dramatic decline with the beginning of the Great Famine in 1845, and dropped below 21 years in the second half of the decade (in 1849 alone, life expectancy fell to just 14 years). The famine came as a result of a Europe-wide potato blight, which had a disproportionally devastating impact on the Irish population due to the dependency on potatoes (particularly in the south and east), and the prevalence of a single variety of potato on the island that allowed the blight to spread faster than in other areas of Europe. Additionally, authorities forcefully redirected much of the country's surplus grain to the British mainland, which exacerbated the situation. Within five years, mass starvation would contribute to the deaths of over one million people on the island, while a further one million would emigrate; this also created a legacy of emigration from Ireland, which saw the population continue to fall until the mid-1900s, and the total population of the island is still well below its pre-famine level of 8.5 million people.

Following the end of the Great Famine, life expectancy would begin to gradually increase in Ireland, as post-famine reforms would see improvements in the living standards of the country’s peasantry, most notably the Land Wars, a largely successful series of strikes, boycotts and protests aimed at reform of the country's agricultural land distribution, which began in the 1870s and lasted into the 20th century. As these reforms were implemented, life expectancy in Ireland would rise to more than fifty years by the turn of the century. While this rise would slow somewhat in the 1910s, due to the large number of Irish soldiers who fought in the First World War and the Spanish Flu pandemic, as well as the period of civil unrest leading up to the island's partition in 1921, life expectancy in Ireland would rise greatly in the 20th century. In the second half of the 20th century, Ireland's healthcare system and living standards developed similarly to the rest of Western Europe, and today, it is often ranks among the top countries globally in terms of human development, GDP and quality of healthcare. With these developments, the increase in life expectancy from birth in Ireland was relatively constant in the first century of independence, and in 2020 is estimated to be 82 years.

Life expectancy in Russia was 29.6 in the year 1845, and over the course of the next 175 years, it is expected to have increased to 72.3 years by 2020. Generally speaking, Russian life expectancy has increased over this 175 year period, however events such as the World Wars, Russian Revolution and a series of famines caused fluctuations before the mid-twentieth century, where the rate fluctuated sporadically. Between 1945 and 1950, Russian life expectancy more than doubled in this five year period, and it then proceeded to increase until the 1970s, when it then began to fall again. Between 1970 and 2005, the number fell from 68.5 to 65, before it then grew again in more recent years.

In 1870, it is estimated that life expectancy from birth in the area of modern-day Iraq was just over the age of 31 years. Life expectancy would remain largely stagnant at this level for much of the late 19th and early 20th centuries, interrupted only by a temporary dip in the late-1910s as the 1918 Spanish Flu epidemic would spread through the region. Life expectancy would begin to rise sharply in the years following the Second World War, however, as rising petroleum sales allowed a rapid modernization of the country, causing access to healthcare and standards of living to rise throughout the country. The large reductions in infant and child mortality were the driving force behind the increase in life expectancy.

This growth would continue steadily until the 1980s, when life expectancy would fall from just under 62 years in 1980, to 58.5 years in 1985, as the decade long Iran-Iraq War would lead to widespread fatalities and displacement in the country. As the fighting eased in the late 1980s, life expectancy began to rise once more in Iraq, reaching 69 years by the start of the 21st century. However, this growth would reverse once more in the 2000s, due to the U.S.-led invasion and occupation of Iraq in 2003, which in turn led to an insurgency of paramilitary and terrorist groups, and the subsequent civil war from 2011 to 2017. As Iraq continues its recovery following four decades of violence and instability, life expectancy is on the rise again, and in 2020, it is estimated that life expectancy from birth in Iraq is over seventy years.

In 1870, the average person born in the Philippines could expect to live to just under the age of 31 years old. This figure would remain unchanged until the early 1900s, when life expectancy would fall to just over 25 years in the Philippine-American War of 1899-1902, as disruptions in food supply and healthcare would result in the loss of several hundred thousand Filipinos to famine and disease. This drop would be accompanied by another drop in the 1920s as the Spanish Flu would ravage the country. However, life expectancy would quickly recover and begin to rise under the United States military administration of the island, as investment by the American government would result in significant expansion in access to nutrition and healthcare. As a result, life expectancy would rise to over 41 years by 1940.

Life expectancy in the Philippines would decline once more in the 1940s, however, in the 1941 invasion and subsequent occupation of the island nation by the Empire of Japan in the Second World War, in which famine and causalities of war would result in the death of an estimated 500,000 Filipinos. Despite significant destruction in the Second World War, and an ending to the bulk of American investment in the country following its independence from the U.S. in 1946, life expectancy in the Philippines would quickly rise in the post-war years as the country would modernize; almost doubling in the two decades between 1945 and 1965 alone. It then plateaued throughout the 1970s and 1980s, during the authoritarian regime of Ferdinand Marcos, before the People Power Revolution in 1986 returned democracy to the country, and living standards began to improve once more. Life expectancy has also increased since this time, and in 2020, it is estimated that the average person born in the Philippines can expect to live to just over the age of 71 years old.

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.

The world's population first reached one billion people in 1803, and reach eight billion in 2023, and will peak at almost 11 billion by the end of the century. Although it took thousands of years to reach one billion people, it did so at the beginning of a phenomenon known as the demographic transition; from this point onwards, population growth has skyrocketed, and since the 1960s the population has increased by one billion people every 12 to 15 years. The demographic transition sees a sharp drop in mortality due to factors such as vaccination, sanitation, and improved food supply; the population boom that follows is due to increased survival rates among children and higher life expectancy among the general population; and fertility then drops in response to this population growth. Regional differences The demographic transition is a global phenomenon, but it has taken place at different times across the world. The industrialized countries of Europe and North America were the first to go through this process, followed by some states in the Western Pacific. Latin America's population then began growing at the turn of the 20th century, but the most significant period of global population growth occurred as Asia progressed in the late-1900s. As of the early 21st century, almost two thirds of the world's population live in Asia, although this is set to change significantly in the coming decades. Future growth The growth of Africa's population, particularly in Sub-Saharan Africa, will have the largest impact on global demographics in this century. From 2000 to 2100, it is expected that Africa's population will have increased by a factor of almost five. It overtook Europe in size in the late 1990s, and overtook the Americas a decade later. In contrast to Africa, Europe's population is now in decline, as birth rates are consistently below death rates in many countries, especially in the south and east, resulting in natural population decline. Similarly, the population of the Americas and Asia are expected to go into decline in the second half of this century, and only Oceania's population will still be growing alongside Africa. By 2100, the world's population will have over three billion more than today, with the vast majority of this concentrated in Africa. Demographers predict that climate change is exacerbating many of the challenges that currently hinder progress in Africa, such as political and food instability; if Africa's transition is prolonged, then it may result in further population growth that would place a strain on the region's resources, however, curbing this growth earlier would alleviate some of the pressure created by climate change.

In 1800, it is estimated that approximately 9.4 million people lived in the region of modern-day South Korea (and 13.8 million on the entire peninsula). The population of this region would remain fairly constant through much of the 19th century, but would begin to grow gradually starting in the mid-1800s, as the fall of the Joseon dynasty and pressure from the U.S. and Japan would end centuries of Korean isolationism. Following the opening of the country to foreign trade, the Korean peninsula would begin to modernize, and by the start of the 20th century, it would have a population of just over ten million. The Korean peninsula was then annexed by Japan in 1910, whose regime implemented industrialization and modernization policies that saw the population of South Korea rising from just under ten million in 1900, to over fifteen million by the start of the Second World War in 1939.

The Korean War Like most regions, the end of the Second World War coincided with a baby boom, that helped see South Korea's population grow by almost two million between 1945 and 1950. However, this boom would stop suddenly in the early 1950s, due to disruption caused by the Korean War. After WWII, the peninsula was split along the 38th parallel, with governments on both sides claiming to be the legitimate rulers of all Korea. Five years of tensions then culminated in North Korea's invasion of the South in June 1950, in the first major conflict of the Cold War. In September, the UN-backed South then repelled the Soviet- and Chinese-backed Northern army, and the frontlines would then fluctuate on either side of the 38th parallel throughout the next three years. The war came to an end in July, 1953, and had an estimated death toll of three million fatalities. The majority of fatalities were civilians on both sides, although the North suffered a disproportionate amount due to extensive bombing campaigns of the U.S. Unlike North Korea, the South's total population did not fall during the war.

Post-war South Korea Between the war's end and the late 1980s, the South's total population more than doubled. In these decades, South Korea was generally viewed as a nominal democracy under authoritarian and military leadership; it was not until 1988 when South Korea transitioned into a stable democracy, and grew its international presence. Much of South Korea's rapid socio-economic growth in the late 20th century was based on the West German model, and was greatly assisted by Japanese and U.S. investment. Today, South Korea is considered one of the world's wealthiest and most developed nations, ranking highly in terms of GDP, human development and life expectancy; it is home to some of the most valuable brands in the world, such as Samsung and Hyundai; and has a growing international cultural presence in music and cinema. In the past decades, South Korea's population growth has somewhat slowed, however it remains one of the most densely populated countries in the world, with total population of more than 51 million people.

It is presumed that the first humans migrated from Siberia to North America approximately twelve thousand years ago, where they then moved southwards to warmer lands. It was not until many centuries later that humans returned to the north and began to settle regions that are now part of Canada. Despite a few short-lived Viking settlements on Newfoundland around the turn of the first millennium CE, the Italian explorer Giovanni Caboto (John Cabot), became the first European to explore the coast of North America in the late 1400s. The French and British crowns both made claims to areas of Canada throughout the sixteenth century, but real colonization and settlement did not begin until the early seventeenth century. Over the next 150 years, France and Britain competed to take control of the booming fur and fishing trade, and to expand their overseas empires. In the Seven Year's War, Britain eventually defeated the French colonists in North America, through superior numbers and a stronger agriculture resources in the southern colonies, and the outcome of the war saw France cede practically all of it's colonies in North America to the British.

Increased migration and declining native populations

The early 1800s saw a large influx of migrants into Canada, with the Irish Potato Famine bringing the first wave of mass-migration to the country, with further migration coming from Scandinavia and Northern Europe. It is estimated that the region received just shy of one million migrants from the British Isles alone, between 1815 and 1850, which helped the population grow to 2.5 million in the mid-1800s and 5.5 million in 1900. It is also estimated that infectious diseases killed around 25 to 33 percent of all Europeans who migrated to Canada before 1891, and around a third of the Canadian population is estimated to have emigrated southwards to the United States in the 1871-1896 period. From the time of European colonization until the mid-nineteenth century, the native population of Canada dropped from roughly 500,000 (some estimates put it as high as two million) to just over 100,000; this was due to a mixture of disease, starvation and warfare, instigated by European migration to the region. The native population was generally segregated and oppressed until the second half of the 1900s; Native Canadians were given the vote in 1960, and, despite their complicated and difficult history, the Canadian government has made significant progress in trying to include indigenous cultures in the country's national identity in recent years. As of 2020, Indigenous Canadians make up more than five percent of the total Canadian population, and a higher birth rate means that this share of the population is expected to grow in the coming decades.

Independence and modern Canada

Canadian independence was finally acknowledged in 1931 by the Statute of Westminster, putting it on equal terms with the United Kingdom within the Commonwealth; virtually granting independence and sovereignty until the Canada Act of 1982 formalized it. Over the past century, Canada has had a relatively stable political system and economy (although it was hit particularly badly by the Wall Street Crash of 1929). Canada entered the First World War with Britain, and as an independent Allied Power in the Second World War; Canadian forces played pivotal roles in a number of campaigns, notably Canada's Hundred Days in WWI, and the country lost more than 100,000 men across both conflicts. The economy boomed in the aftermath of the Second World War, and a stream of socially democratic programs such as universal health care and the Canadian pension plan were introduced, which contributed to a rise in the standard of living. The post war period also saw various territories deciding to join Canada, with Newfoundland joining in 1949, and Nunavut in 1999. Today Canada is among the most highly ranked in countries in terms of civil liberties, quality of life and economic growth. It promotes and welcomes immigrants from all over the world and, as a result, it has one of the most ethnically diverse and multicultural populations of any country in the world. As of 2020, Canada's population stands at around 38 million people, and continues to grow due to high migration levels and life expectancy, and a steady birth rate.

The total fertility rate of the world has dropped from around five children per woman in 1950, to 2.2 children per woman in 2025, which means that women today are having fewer than half the number of children that women did 75 years ago. Replacement level fertility This change has come as a result of the global demographic transition, and is influenced by factors such as the significant reduction in infant and child mortality, reduced number of child marriages, increased educational and vocational opportunities for women, and the increased efficacy and availability of contraception. While this change has become synonymous with societal progress, it does have wide-reaching demographic impact - if the global average falls below replacement level (roughly 2.1 children per woman), as is expected to happen in the 2050s, then this will lead to long-term population decline on a global scale. Regional variations When broken down by continent, Africa is the only region with a fertility rate above the global average, and, alongside Oceania, it is the only region with a fertility rate above replacement level. Until the 1980s, the average woman in Africa could expect to have 6-7 children over the course of their lifetime, and there are still several countries in Africa where women can still expect to have five or more children in 2025. Historically, Europe has had the lowest fertility rates in the world over the past century, falling below replacement level in 1975. Europe's population has grown through a combination of migration and increasing life expectancy, however even high immigration rates could not prevent its population from going into decline in 2021.