Gen Zers are less likely to have at least one kid than older generations were at the same age. Rawlstock/Getty Images

Birth rates in the US have been falling for decades, but there's been an especially large drop in the likelihood of Gen Zers in their 20s having a kid compared with their older peers at the same age.

For 26-year-old Gen Zers, the likelihood of having at least one kid was 26%, down from 47% for millennials , 50% for Gen X, and 46% for boomers at that age. There were also differences between Gen Z and older generations in the probability of wanting another kid.

That's based on an analysis by a group of researchers published by the Federal Reserve Bank of Atlanta. Julie Hotchkiss, a research economist at the Atlanta Fed, told Business Insider the analysis controls for education, partnership status, and some health conditions.…