Which is the biggest generation in the British population?

It must be the Baby Boomers, right? It certainly was once: more babies were born in 1947[1] than in any year before or since, and that cohort remained the most numerous even through the secondary peak in births that occurred in 1964-65[2]. Those two peaks in births meant that for more than six decades the biggest single-year cohort in the population was either people born in the late-1940s or born in the mid-1960s. But no longer…

The Generation Gain

Since 2020 the mantle of biggest cohort in the British population has been held by the 1988 birth cohort, even though the number of babies born in the country that year was not strikingly high[3] – at least in comparison to 1947 and 1964-65. While the size of the Baby Boomer cohort is predominantly a story of births (as the label suggests), the large number of people in today’s population who were born in 1988 is at least as much a story of migration.

A historical characteristic of demographic trends, viewed over the long-term, are their predictability. If we know the number of people aged zero in the population, we can often make an accurate prediction of the number of 18-year-olds there will be in the population 18 years later, and from there predict the size of that cohort at (say) age 34. This was certainly true of the cohort born in the mid-1960s: their numbers grew by just 0.2% from age 0 to age 18, then declined by just 1% between 1983 (when they were 18) and 1999 (when they were 34). Among this cohort, moderately positive net migration (both as children and as young adults) largely offset the depleting effect of deaths.

Among the 1988 cohort net migration into Britain was higher: at the age of 18 this cohort was 2.5% more numerous than they were in their year of birth: deaths in childhood were declining through the 1990s, while migration into Britain was on the increase. The change during young adulthood was much more dramatic: by 2022 there were more than 846,000 people aged 34, an increase of 20% on the 1988 cohort’s size in 2006 (when they were 18).

The 1988 cohort is no outlier either – similar characteristics are apparent as far back as the 1977-born cohort: a gradual net increase in numbers through the childhood years giving way to much more rapid growth in numbers when in their twenties. But there were fewer births in Britain in 1977[4] than in any other year since WW2, so even in combination with an increasing number of 1977-born migrants the size of the 1977 cohort in Britain’s population has remained relatively small. The 1980s-born generation can fairly be characterized as both a high-births generation and a high-migration generation, with 1988 being the cohort when the combined effect of these two population dynamics peaked.

What does this mean?

So what does it mean when the largest ‘bulge’ in Britain’s population pyramid is a reflection not only of high number of births (as was the case with previous ‘bulges’) but also large numbers of people moving to Britain during either childhood or young adulthood? One impact is that generations born in Britain since 1980 grew up in more multi-cultural environments than their forbears, and this likely affected their views and attitudes. We know that the attitudes held by the generations born after 1980 are quite different, across a range of measures, to those held by the generations born in the preceding three or four decades – not least a world-view that tends more internationalist.

In an election year, might this late-1980s cohort actually have more power-in-numbers than we realise? Will they, purely by virtue of their numbers, become the main focus of political manifestos as the Baby Boomers have been in past elections? Perhaps; and perhaps not. Not all of the 1988-born cohort that currently lives in Britain will be eligible to vote in the next General Election, for example many of those who migrated as adults from EU countries are likely to be ineligible, which will reduce the voting size of the 1988 cohort. This is also likely to be further reduced by a lower propensity to vote among this cohort than among (say) the 1947 cohort.

Nevertheless for anyone interested in looking beyond the narrow confines of British party politics – and the myopic focus of a General Election campaign – Generation-1988 is likely to become more important. Partly that is just a numbers game: as late-1940s and mid-1960s cohorts decline in number, the relative prominence of Gen-88 will increase. But the reasons for Gen-88’s large numbers are just as important: population dynamics combined to make today’s most numerous generation more diverse and more internationalist – both in background and outlook – than the previous generations to hold the mantle of biggest cohort.

The passing of the mantle ‘biggest cohort’ to Gen-88 in 2020 also marked the start of a change in the population overall – from a society driven by Baby Boomer priorities to one which reflects the (quite different) outlook held by those who were still children at the turn of the millennium. Anyone wishing to market to a population in which this cohort holds increasing sway will need to accommodate this cohort’s broader diversity (compared to earlier large generations) and reflect how Gen-88’s outlook differs from their forbears.


[1] There were 881,026 births in England and Wales in 1947

[2] There were 875,972 births in 1964, and 862,725 births in 1965, in England and Wales

[3] There were 693,577 births in England and Wales in 1988

[4] There were 569,259 births in England and Wales in 1977

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