[Updated] APA Membership Goes from 2.4% to 5.4% Self-Reported Black or African-American in a Single Year?

Update, Feb. 11: After I posted the below, Amy Ferrer at the APA looked into it and discovered that it was a spreadsheet error. The corrected data are here. In the corrected data, the 2014 percentage is 2.4% and 2015 is 2.6%, well within chance variation.

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I'm looking at this table of demographic statistics from the American Philosophical Association, comparing the number of APA survey respondents self-describing as "Black/African-American", among regular APA members (excluding emeritus, K-12, colleague, international, and student members). In 2014, I see 56 out of 2730 respondents (2.1%; 2.4% if we exclude those in the "prefer not to answer" category) in the "Black/African-American" category. In 2015, it's 146 out of 2874 (5.1%; 5.4% excluding "prefer not to answer").

It's not possible that the percentage of Black philosophers in the U.S. doubled in a single year. Since only about half of the APA membership responded to the survey, it could be a non-response effect (i.e., Black philosophers much more likely to respond in 2015 than in 2014), but if so it's an amazingly huge one. Another possibility is a change in the format of the question or in the willingness of members to describe themselves as belonging to this racial category -- but if so, again it's quite large for an effect of that sort in such a short time frame.

Thoughts?