The triangular (pyramid) shape of the graph is typical of a population with high birth and death rates - there are many more young people than older people. The Total Fertility Rate - the average number of children that would be born to a woman over her lifetime - was around 2.8, much higher than it is today.
Out of every 1,000 babies born in 1911, 130 died before reaching their first birthday. About one death in every four in the whole population was of an infant before its first birthday.
Life was short compared to today and infectious diseases were the main cause of death. Life expectancy at birth in 1911 was 49 years for men and 53 years for women.
The graph also shows higher numbers at ages ending in zero (30, 40, 50, 60, etc). This is known as 'age heaping' and occurs where age rather than date of birth is collected and people report rounded ages.
Ten years on, the graph still shows a predominantly youthful population. However, two major events have affected the shape of the graph:
First, World War I (1914-18). The male side of the graph between ages 20 and 40 has changed, representing the 723,000 British servicemen who lost their lives. The war also led to a dip in births, with smaller cohorts born between 1914 and 1918. The end of World War I saw a rapid rise in births, with large cohorts aged 0 and 1 in 1921.
Second, the 1918-21 influenza pandemic. This unusually severe strain of influenza caused 152,000 excess deaths between June 1918 and May 1919 alone. Most of these were infants, children, and adults aged under 40.
Better public health measures, childcare and hygiene had begun to improve infant survival. Deaths to under-ones had fallen to 83 per 1,000 by 1921. Survival rates at older ages had also improved. Life expectancy at birth was 56 years for men and 60 years for women.
The shape of the graph is now less triangular, indicating a population with lower birth and death rates.Notice that the graph at around age 10 years is significantly wider than for the younger ages below. The widest point represents the rapid increase in births following the return of men from World War I. However, World War I left a shortage of marriageable men, leaving many women at early childbearing ages single and childless. Thus at ages younger than 10 we can see smaller population sizes reflecting lower fertility. The Total Fertility Rate had fallen to 1.9. However, the decline in fertility could also be seen as the continuation of the longer-term trend, with the shift from a high fertility/high mortality population to a low fertility/low mortality population.
Improved public health and changing childcare practices had continued to lower the infant death rate to 66 per 1,000 babies born. Survival rates at older ages had continued to improve. Life expectancy at birth was now 58 years for men and 62 years for women. The rounder shape of the top half of the graph reflects a noticeable decline in deaths among people aged 55 to 74.
There was no census in 1941 because of World War II, so the 1951 Census highlights 20 years of change.
The lower number of births in the 1930s, (in part as a result of the economic recession), and deaths in World War II had changed the shape of the lower half of the graph completely. For the first time we can also see the immediate post-World War II baby boom. More people were living longer, especially women. Note the rounding of the top half of the graph.
The impact of the National Health Service (NHS), introduced in 1948, had begun to contribute to improving survival rates among all age groups. The post-war National Food Policy, improving environmental conditions and the use of more effective medications (including antibiotics) also helped improve survival rates among the young.
Infant death rates had fallen steadily to only 30 per 1,000. Life expectancy at birth in 1951 was 66 years for men and 71 years for women.
By 1961, the shape of the graph has changed again - there is now less of a size difference between the age bands, apart from the two post-war baby booms, until we get to the older age groups. The graph now shows an older population with lower death rates. Most deaths are now due to degenerative conditions such as heart disease, cancers and stroke, rather than infectious diseases.
A NHS programme to vaccinate everyone under the age of 15 against polio and diphtheria started in 1958. This helped to boost survival rates for this younger age group and, over time, improved survival rates at all ages. Survival rates for men aged between 45 and 64 were now catching up with those of women.
At the bottom of the graph, the baby boom that began in the late 1950s/early 1960s can be seen: the Total Fertility Rate was back up to 2.8 children, a similar level to 1911. Infant death rates have fallen to 21 per 1,000 born. Life expectancy at birth was 68 years for men and 74 years for women.
The baby boom which began in the late 1950s/early 1960s and peaked in around 1964 has boosted numbers in the younger part of the graph. And its impact is made all the more obvious by the small birth cohorts of the 1930s and the low number of births during World War II.
By 1971, the Total Fertility Rate had fallen to 2.4. There were now more means for women to control their fertility with the introduction of the 1967 Abortion Act and the availability (although initially primarily to married women) of new effective forms of birth-control such as the contraceptive pill.
At older ages, many of the effects referred to previously such as the 1918-21 influenza pandemic and the post-World War II baby boom are still visible on the graph.
More people were living longer and fewer babies were dying - 18 out of every 1,000 died before their first birthday. Life expectancy at birth in 1971 was 69 years for men and 76 years for women.
The shape of the graph has changed again, reflecting a falling birth rate and higher survival rates among all age groups, but with improvements being seen in survival particularly at older ages.
During most of the 1970s, fertility continued to fall. Control of fertility was assisted when, in 1974, the NHS made free contraception available to all women. By 1981, the Total Fertility Rate had fallen further to 1.8 children per woman.
Infant deaths also fell to 11 per 1,000 and survival rates among older people improved too - there are now noticeably wider age bands at ages 65 and over.
Life expectancy at birth in 1981 reached 71 and 77 years for men and women respectively.
The post-World War II and 1960s baby boomers are outward steps on what is otherwise a graph with very little difference in the size of successive generations up to ages in the early 70's.
However, births gradually increased throughout the 1980s. This was due to the very large birth cohort of 1960s baby boomers beginning to have children.
Public awareness campaigns and continued medical innovation (for example, breast cancer screening for all women aged 50-plus in 1988) acted to improve survival rates at all ages.
Infant deaths had fallen to seven per 1,000 and life expectancy at birth was now 73 years for men and 79 years for women.
The shape of the graph is similar to 1991, but notice a slight tapering at the bottom, reflecting the lower birth rates of the 1990s. The Total Fertility Rate in 2001 was 1.6. The infant mortality rate had also continued to fall, with fewer than six babies dying before their first birthday for every 1,000 born (remember, it was 130 per 1,000 in 1911). Life expectancy at birth in 2001 was 76 years for men and 81 years for women.
We can still see most of the trends revealed in earlier censuses reflected in the shape of the 2001 graph. The baby boomers from the years following World War I, World War II and the 1960s are clearly visible.Also apparent is the impact of small birth cohorts arising from World War I (1914-18), World War II (1939-45) and the 1970s. To a lesser extent the effect of the 1918-21 influenza pandemic and the 1930s economic depression can still be seen.
The effects of events from the early part of the last century, including World War I and the 1918-21 influenza pandemic, are diminishing as many of the affected people are now deceased. Effects of events later in the century such as the immediate post World War II baby boom, the 1960s baby boom and lower numbers of births in the 1970s are still clearly visible.
From 2001 to 2011 there were high levels of net inward migration, reflected in the widening of the graph at younger working ages. In part this was driven by the expansion of the European Union in 2004 and 2007. Whereas in 2001 the bottom of the graph was tapering, the graph is now widening. This indicates a period with an increasing number of births, which was driven by the immigration of women of childbearing age (15-44) into England and Wales and rising fertility among UK-born women. Life expectancy at birth in 2011 stood at 79 years for men and 83 years for women. Infant mortality was the lowest recorded at 4 deaths per 1,000 live births.