Your personal anecdote would be, more or less, consistent with their findings... "there are no significant differences in birth rates when a woman has two chil

Your personal anecdote would be, more or less, consistent with their findings... "there are no significant differences in birth rates when a woman has two children where just one requires a carseat." That said, I don't think this is anything more than a correlation; not even a strong correlation (requiring many caveats, controls, and cofactors), and to me that effect size seems nominal.