Population of the UK 1990-2023, by generation

In 2023, there were approximately 14.69 million millennials in the United Kingdom, making it the largest generational cohort at that time. Millennials surpassed the Baby Boomer generation as the largest generation for the first time in 2019. The two youngest generations, Gen Z and Gen Alpha, numbered approximately 13.2 million, and 8.3 million respectively. Gen X are, as of the most recent year, the second-largest generation in the UK at 14.04 million people, with their parent's generation, the Silent Generation, numbering around 4.3 million people in the same year. There were estimated to be 85,920 people who belonged to the Greatest Generation, the parents of the Baby Boomer generation, who lived through major events such as the Great Depression and World War Two. 

Post-War Baby Boom

The baby boomer generation was the largest generation for much of this period due to the spike in births that happened after the Second World War. In 1947 for example, there were over one million live births in the United Kingdom, compared with just 657,038 live births just thirty years later in 1977. Members of this generation are typically the parents of millennials, and were the driving force behind the countercultural movement of the 1960s, due to their large numbers relative to older generations at the time. The next generational cohort after Boomers are Generation X, born between 1965 and 1980. This generation had fewer members than the Boomer generation for most of its existence, and only became larger than it in 2021.

Millennials and Gen Z

As of 2022, the most common single year of age in the United Kingdom in 2020 was 34, with approximately 944,491 people this age. Furthermore, people aged between 30 and 34 were the most numerous age group in this year, at approximately 4.67 million people. As of 2022, people in this age group were Millennials, the large generation who came of age in the late 1990s and early 2000s. Many members of this generation entered the workforce following the 2008 financial crash, and suffered through high levels of unemployment during the early 2010s. The generation that followed Millennials, Generation Z, have also experienced tough socio-economic conditions recently, with key formative years dominated by the COVID-19 pandemic, climate change, and an increasingly unstable geopolitical situation.