The chart shows the annual rate of global population growth according to historical estimates and projections from the UN World Population Prospects.
The growth rate peaked in 1963 at over 2% per year, and since then, it has more than halved, falling to less than 1% by 2020.
The UN demographers expect rates to continue falling until the end of the century, eventually leading to negative growth rates and a shrinking global population.
Source: Our World in Data.
What makes u think the prediction is based on the Baby Boomer Generation? I think the prediction is very much rather based on how the fertility rate drops the further a country develops. Higher education levels and better living conditions have shown to reduce the fertility rate in western countries, and now that developing countries are catching up, we can expect (and we see that already) that their fertility rates are dropping as well, hence being a good basis to estimate the future total population numbers.