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.

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.

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.

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.

In 1880, the average person born in the area of modern-day South Korea could expect to live to just under the age of 26, a figure which would remain below thirty until the 1920s. Life expectancy would fall to its lowest level of just 24 years in 1920, however, as the 1918 Spanish Flu epidemic would spread through the country, resulting in an estimated 200,000 deaths across the Korean peninsula. Life expectancy would begin to rise in the 1920s, however, as development programs by the Japanese colonial administration would see economic growth and access to healthcare improve greatly in the region. The 1940s and 1950s would see a slowing, then a reversal to this growth though, as the final years of the Second World War, and later the 1950 Korean War, would see significant destruction and fatalities in the country.

Following the end of the Korean War with the 1953 armistice, life expectancy would begin to climb again in the newly-established South Korea, as the country would begin to rapidly modernize and improve access to healthcare and nutrition, raising standards of living and cutting child mortality rates throughout the country. As a result, life expectancy would rise from just under 47 years in 1950, to over 75 years by the turn of the century. This rise in life expectancy has continued steadily into the 21st century, and as a result, in 2020, it is estimated that the average person born in South Korea will live to just under the age of 83 years, one of the highest life expectancies in the world.

Study of disease in the past can help illuminate patterns of human health, disease, and aging in the present. As average human life expectancy and incidence of chronic disease have increased in the last century, efforts to understand this epidemiologic shift have led to more investigation of healthy aging. Using osteological and radiological methods of analysis, this study examined 212 mostly nineteenth century adult skeletons from the crypt of St. Bride’s in London, in order to investigate the relationship between age-at-death, sex, and number of lesions observed in bone. Lesions were classified into macro-level categories according to the Rapid Method for Recording Human Skeletal Data, and the correlation between age group and number of lesions in each category, as well as the total number of lesions, were analyzed. Correlations between age-at-death and the number and type of lesions were compared across both methods of analysis. A greater total number of lesions and a greater number of types of lesions was observed for the osteologically analyzed data, compared to the radiologically analyzed data. Correlations between age-at-death and specific pathology groups were in general weak, though stronger for the osteologically analyzed data. For each method of analysis, there were statistically significant differences between the total number of lesions and age group, with total number of lesions increasing with age, regardless of method of analysis. Joint and metabolic lesions were the most significant predictors of age-at-death. The correlations between total lesions observed and age-at-death were similar for radiologically and osteologically analyzed data, for the same set of bones. This suggests that, for the bones analyzed, while the number of lesions recorded differed according to method of analysis, the relationship between overall observed lesion burden and age-at-death was similar for both osteological and radiological analysis.

In 1875, the average person born in Chile could expect to live to the age of 32 years, a figure that would remain largely stagnante throughout the late 19th and early 20th century, as the country’s Parliamentary era would see relatively little change in the day to day lives of the country’s citizens. Outside of two dips in 1910 and 1920, the latter primarily driven by the 1918 Spanish Flu epidemic. Life expectancy would see two sharp increases following the end of the First World War; the first in the 1920s, and the most dramatic in the early 1950s.

The first of these spikes, under President Ibáñez del Campo, can be attributed primarily to large increases in spending on public healthcare and improvements in public sanitation by the Campo administration. The second and larger spike, under President González Videla, can be attributed to a combination of mass immunization and vaccination, and the implementation of a national health care system, drastically cutting child mortality in the country. As a result of these reforms, life expectancy in Chile would more than double in just thirty years, rising from just over 33 years in 1925 to 69 years by 1955. Following the end of the Videla administration in 1952, life expectancy would continue to rise in Chile, as increasing urbanization, and the successful eradication of many childhood diseases would see both child and overall mortality decline. This rise has continued even into the 21st century, and as a result, life expectancy in Chile rose to over 78 years by the end of the century, and in 2020, it is estimated that the average person born in Chile will live to over 82 years old, the highest in South America.

In 1870, the average person born in Colombia could expect to live to the age of 32 years old, a figure which would see only marginal increase in the country until the 1930s (with a minor decline in 1920 from the 1918 Spanish Flu epidemic). However, life expectancy would begin to increase rapidly starting in the 1930s, as a series of reforms and modernization programs following the Great Depression, combined with a relatively quick recovery from the financial crisis, would see significant improvements in standards of living and access to healthcare in the country. As a result, life expectancy would increase by nearly twenty years between 1930 and 1950 alone, and this would continue at an accelerated rate through much of the remainder of the century. While the economic and political instability resulting from the increased drug cartel and government clashes of the 1990s would see a pause in life expectancy growth, increases have largely resumed in the 21st century, and in 2020, it is estimated that the average person born in Columbia can expect to live to just over 77 years old.

In 1875, those born in the present-day region of Indonesia lived to an averae age of thirty years. This figure would remain largely stagnant until the 1910s, where the the 1918 Spanish Flu epidemic would cause life expectancy to fall to just 27 years as the epidemic spread across the region. Following the end of the Spanish Flu epidemic in 1920, life expectancy would begin to rise in Indonesia, as public works and infrastructure programs by the Dutch colonial administration would see standards of living begin to rise in the country. However, after peaking at 36 years in 1940, life expectancy would fall to just thirty years once more with the invasion and subsequent occupation of the island by the Empire of Japan in 1942; most estimates suggest that between 2.4 and four million people in Indonesia died from famine, forced labor and violence during the Second World War.

Life expectancy would begin rising following the country’s independence from the Dutch in 1949, particularly in the early 1950s as mass immunization and vaccination, combined with rapid modernization would see child mortality and standards of living rise throughout the remainder of the century, reaching over 65 years by the turn of the millennium. This rise in life expectancy has continued in the 21st century, and in 2020, the average person born in Indonesia is expect to live to beyond the age of 71 years.

In 1870, the average person born in Ecuador could expect to live to just under the age of 33. Outside of a temporary drop in the late 1910s, the result of the 1918 Spanish Flu epidemic, life expectancy in Ecuador would see only modest growth for much of the first half of the 20th century, reaching just over 35 years in 1940. However, life expectancy would begin to rise sharply in the 1940s, as reforms under President Galo Plaza Lasso would bring a period of stability and economic growth to the country, greatly improving standards of living and seeing the infant mortality rate drop dramatically. Between 1940 and 1950 alone, life expectancy would jump by more than twelve years, to almost 48 years.

Following the end of Galo Plaza’s term in 1952, Ecuador would endure a period of instability and civil unrest, causing life expectancy to temporarily stagnate for several years. However, life expectancy would begin to grow rapidly again starting in the 1960s as modernization would see a continuation of the improvements made in the 1940s. This growth would continue steadily into the 21st century, and in 2020, life expectancy from birth is almost 77 years.

In 1870, life expectancy from birth in the modern-day territory of Iran was approximately 25.6 years. This figure would see little change in Iran for much of the late 19th and early 20th century; the only major change was the dip in the late 1910s, resulting from the 1918 Spanish Flu epidemic) and a famine from 1918 to 1919, which led to significant fatalities across the region. Life expectancy would begin to grow rapidly in the 1940s, as the country’s oil reserves, discovered in 1908, would see an economic boom in the years during and immediately following the Second World War, providing a valuable source of funding for socio-economic reforms implemented under Reza Shah. This, in turn, saw a rapid modernization of healthcare in the country, as well as the implementation of mass vaccination programs in the early 1940s, which greatly lowered child mortality rates and allowed life expectancy to rise.

As implementation of these programs would continue, life expectancy from birth rose from just over 27 years in 1940, to approximately 39 years in 1950. After the end of the rapid growth of the 1940s, life expectancy would continue steadily rise until 1980, peaking at 56.7 years. However, life expectancy would fall to just 52 years in 1985, the result of mass fatalities in the Iran-Iraq War of 1980 to 1988. Following the war’s end with a UN-brokered ceasefire in 1988, life expectancy would quickly recover, reaching over 69 years by the turn of the century. Life expectancy has continued to rise throughout the 21st century, and it is now estimated that the average child born in Iran in 2020 will live to the age of approximately 76 years.

In 1870, the average child born in Peru could expect to live to just under the age of 36 years old. This figure would decline slowly throughout the late 19th and early 20th centuries, as internal and regional conflicts and economic instability would disrupt and hinder the advancement of Peruvian healthcare. The relatively sharp dip in the late 1910s can be attributed to the 1918 Spanish Flu epidemic. Life expectancy would begin to rise in the 1940s, however, a thriving economy and a series of populist policies implemented in this period would see living standards rise across much of the country.

Life expectancy has continuously grown since the 1940s, although at a slower rate than in the 1940s and 1950s. Healthcare advancements and mass immunization have been the driving forces behind Peru's increased life expectancy, due to the drastic decline in child mortality. This growth has continued into the 21st century, despite political and economic turmoil in recent years, and in 2020, it is estimated that the average person born in Peru will live to just over the age of 76 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 1880, the average person born in the area of modern day Yemen could expect to live to just over the age of 23, a rate which would remain largely unchanged throughout the end of the 19th and first half of the 20th century (outside of a small dip from the Spanish Flu in the late 1910s). However, life expectancy in Yemen would begin to rise greatly in the 1950s, as Imam Ahmed would open up the country from its isolationist policies, allowing for a significant expansion in economic growth and improvements to healthcare and living standards. Yemen’s growing oil revenues fueled these developments, resulting in life expectancy more than doubling by the end of the century. However, life expectancy would slow and ultimately stagnate in the 21th century, as the Yemeni Civil War would continue to cause significant disruptions in healthcare services and severe famine in the country. As a result, it is estimated in 2020 that the average person born in Yemen can expect to live to just over the age of 66 years old.

Bulgaria's life expectancy from birth was just 36 years at the beginning of the nineteenth century, and it increased to 40 years by the beginning of the twentieth century (the consistency of this increase suggests that the figures are based on the average for the 1800s). Life expectancy then increased to 43.8 years by 1915, before the First World War and Spanish Flu Pandemic caused it to fall by almost two years. Apart from a small decrease in the 1940s, due to the Second World War, Bulgaria's life expectancy then grew to 70 years in the 1960s, where it plateaued around 71 until the 2000s. In the past two decades, life expectancy has increased again by almost four years, reaching almost 75 years in 2020.

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.

In 1865, the average person born in Bangladesh could expect to live to just over the age of 25 years old. This figure would gradually decline throughout the remainder of the 19th century, falling to just over 20 years by 1900, as the Bengal region of British Raj would see several severe famines in this time period. However, life expectancy would begin to increase gradually in the early 1900s, outside of a small decline in the late 1910s from the 1918 Spanish Flu epidemic. Beginning in the 1930s, life expectancy in Bangladesh would begin to grow rapidly, as wartime exports and industrialization would lead to significant improvements in standards of living in the region. This growth would continue steadily throughout the rest of the century, declining only with the Bangladesh War of Independence in 1971. As access to and quality of healthcare in Bangladesh continuously improves, in 2020, the average person born in Bangladesh can expect to live to just over the age of 72 years old, which is higher than most other countries on the Indian subcontinent.

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.