According to this study[0] - and if experts are to be believed - it's not zero (in the case of B-W differences). "Around 90% of experts believed that genes had

According to this study[0] - and if experts are to be believed - it's not zero (in the case of B-W differences). "Around 90% of experts believed that genes had at least some influence on cross-national differences in cognitive ability." [0]http://journal.frontiersin.org/article/10.3389/fpsyg.2016.00399/full http://journal.frontiersin.org/article/10.3389/fpsyg.2016.00...