Literally a guess. I've worked with very few sites that target older consumers, so my data points are limited, but in one of these the bounce rate dropped by more than 20% (home decor industry).

Unlike more recent experimentations, I did not conduct a formal AB/multivariate test, but the font size had been the only internal change at the time. Also, I have no idea whether these lower bounce rates translated into higher revenue.

Also, all of the sites mentioned above were female-oriented.