Pretty much everyone has been a net beneficiary, not just the Boomer generation. The Silent Generation who financed the establishment of the welfare state are the only ones not.
Because the modern welfare state developed as they were in older working age, cohorts that have now mainly reached the end of their lives – members of the forgotten generation (born 1896-1910) and the oldest two-thirds of the greatest generation (1911-25) – emerge as clear net beneficiaries. Measured relative to GDP per capita, these cohorts’ average
withdrawals were at least 25 per cent higher than their contributions. The silent
generation (1926-45), however, were mostly in early working age during the establishment of the modern welfare state from the late-1940s onwards. This means that the increased spend on education for subsequent cohorts, along with health and pension provision they were taxed to fund for other cohorts, was almost greater than the support they received themselves, leaving them with ‘net withdrawals’ of 5 to 15 per cent.
To consider the lifetime position of younger cohorts that have not yet reached old age we are required to make big assumptions about the future path of tax and spending. In the first instance we follow John Hills’ approach and assume that taxes collected in any given year are sufficient to fund welfare spending in that year, and that this spending takes up a growing share of GDP, largely due to growing health spend, as long-term Office for Budget Responsibility (OBR) projections suggest it will. Under these assumptions, cohorts from the baby boomer generation (1946-66), generation X (1966-80) and the millennial generation (1981-2000) all have higher net withdrawals than the silent generation, of around 20 to 25 per cent.
https://www.resolutionfoundation.org/app/uploads/2018/02/Generational-welfare.pdf