I scan read the paper. • It seems OK. Large sample size, fairly simple statistical treatment, clear and (mostly) honest writeup of their results. • About half

I scan read the paper. • It seems OK. Large sample size, fairly simple statistical treatment, clear and (mostly) honest writeup of their results. • About half of reviewers could correctly guess who the authors were despite the double blinding. • The motivation was the widespread belief in their field that women are discriminated against by peer review. In reality they found a slight bias in favor of women. (Their abstract and press release says they found no bias, but on p11 they say differently). • They also found no racism. Review results for people from non-western countries didn't change. • The difference is all due to a strong positive bias towards researchers from rich countries. This is probably "prestige bias", but can also just be that people go softer on people they know already because the reviewers are mostly western. • Optional double blinding will therefore be ineffective, it has to be mandatory.