I see that the question of Jewish ethnocentrism has been raised again in HBD World, so I thought I would look at it from another angle with the MIDUS Study. Participants were asked: "How important do you think it is for people of your religion to marry people who are the same religion?" Answers ranged from "very" (4) to "not at all" (1). Here are the means by affiliation:
Jews are between members of sects and denominations in the importance they place on marrying within the faith. The differences on the table are striking. For example, the gap between the means for Jews and Unitarians is 1.4 standard deviations--a huge difference.
I include the standard deviations as a measure of agreement within each group. Jehovah's Witnesses (JWs) and Unitarians have two of the lowest numbers: this indicates that JWs have a comparatively high level of agreement that they should marry other JWs, while Unitarians agree that endogamy is unimportant. You can see that the SD for Jews is high, which indicates a broad diversity of opinion on the question. So Jews are comparatively "religiocentric" but not monolithic.