Came across this meta analysis The Jewish Advantage: Jews are Intelligent and High-Achieving, that suggests Jewish high achievement is due to 9-15 point IQ advantage over gentiles.
Regarding the first question, Lynn has supplied a wealth of data suggesting that the average IQ of Ashkenazi Jews is between 109 and 115 depending on the type of cognitive battery they’re tested with. Lynn also provides some data on the IQs of Mizrahim, Sephardim, and Ethiopian Jews. The IQs of the Mizrahi are indistinguishable from Arabs, centering around 87 when sampled together, Sephardim have IQs of around 100, and Ethiopian Jews have an average IQ of 69. For comparison, White Gentiles have IQs of around 100. Their high average IQ makes Ashkenazi Jews the most intelligent group for which there are data sufficient to form such a conclusion. The 12-point advantage of Jews is seen in every country in which they reside; it carries with them whether they’ve moved to America, Russia, Latin America, or Israel. (It is important to note that the myth of low Jewish IQ at Ellis Island is just that — a myth; see Rushton, 1997; Snyderman & Herrnstein, 1983, 1985; the low national IQ of Israel is plausibly explained by the fact that the population is only partially Ashkenazi.).
Jewish IQ advantage is not a new observation, but this is the most extensive write-up I have seen on the topic.
There a ton of information in here, not just about Jewish IQ but about ‘g’ and how it correlated with other variables.
A question is, how important are cultural factors for Jewish high achievement, although the article does not cover this in as much detail. This passage suggests it plays some role, but how much is hard to ascertain:
Jews attach more importance to four values than non-Jews: Considerateness, interest in how and why things happen (curiosity), judgment, and responsibility. It is difficult to see how these could impact Jewish achievement: “The results that Jewish parents are more likely to foster interest in how and why things happen suggest that this might contribute to the high Jewish achievement in science, but Jews have been equally successful in law, the humanities and business, for which an interest in how and why things happen would not seem to confer any obvious advantage.”
An important question is, how successful are 115+ IQ Jews relative to 115+ IQ Catholics and Protestants? If much more so, then cultural factors play an important role. I suspect, after adjusting for IQ, Jews are much more successful in terms of income, preeminence in government, science, business, and law, and academic achievement. It would have to be that way considering that there are so few Jews in America yet they are so over-represented, even after adjusting for IQ. 61% of the U.S. population are non-Hispanic white, so excluding Jews means 59% of Americans are white Christians, yet Jews are 6-8% of Congress. Despite the Jewish IQ advantage, there are still going to be more high-IQ gentiles than high-IQ Jews, because there are so few Jews. 29 million non-Hispanic white Christians in America have IQs above 115 and four million have IQs above 130, yet four of the past eight Chairman of the Federal Reserve are Jewish. My hypothesis for this is that high-IQ people do better in less structured environments, and the trend over the past half century of increasing secularism in the Jewish population means smart Jews are not as constrained by cultural and religious obligations, whereas smart gentiles are.