Countries are resurveyed every "wave". How this data is reflected in that map, I'm not qualified to say: the most recent survey? Some kind of averaging of all the surveys conducted in that country? Not all countries have participated in every wave. Some have been only in the last, and more countries will be added (specifically, Inglehart and Welzel intend to include more Islamic countries in the next survey for the first time).

Well, this may turn out to be the next incarnation of social darwinist type theorizing, I'll update you a few years from now :)

"It Can't Be Just About Us"
--Frank Schnittger, ETian Extraordinaire