I suspect the reason for the increase in the percentage of runners meeting the standard in the most recent years is the introduction of the Nike Zoom Vaporfly 4% in 2017, followed by other running shoe brands. They definitely help one run faster.

If the current women's marathon World record (mixed gender events) is 10% slower than the men's World record, then the Boston open qualifying time seems generous to women (17% slower). Indeed, I used to think this was by design, to encourage women participation - your analysis suggests this is not really the case.

Similarly, without looking at the analysis I used to believe that the BQ times became more lenient as one aged, to encourage older participation - if a runner stayed with the sport long enough they'd eventually meet the qualifying time! But, sample of one, I met the qualifying time two age groups ago, and ran Boston in 2016, but am now well off the standard :(

Thanks Brian, good article!