Who is more cliquish: blacks or Jews? I'm interested in the question of how much people prefer the company of their own to that of other groups. The General Social Survey provides answers when it asks about the religion and race of your best friend. If minorities did not prefer their own company, we would expect them to frequently have an outsider as a best friend because, as a member of a small group, they are are surrounded by a sea of opportunities to befriend members of the majority. The smaller the group, the more out-members you will bump into during your daily routine. If, on the other hand, you strongly prefer your own, you will swim against this tide of opportunity and seek out as a best friend a member of the in-group. For majority members, even if they had no preference for their own, we would expect most of them to end up with majority friends because they too are surrounded by members of the majority. Even if you wanted to, it is difficult to find a Jewish best friend in Boise.
These are the percent of people whose best friend is of the same faith:
Jews are as likely to have a best friend of the same religion as are Protestants, even though Protestants are 29 times larger (58% versus 2%). Jews are more likely to have a co-religionist as a best friend than are Catholics, even though Catholics are a much larger group (27% versus 2%).
Let's now look at race. Here are the percentages of people having a same-race best friend:
Blacks are almost as likely to have a same-race best friend as whites, even though whites are 6 times are numerous (80% versus 13%).
So to answer the question in the title? One complicating factor here is that blacks are more segregated than Jews, so it more difficult for a black person to make a white friend. Another complicating factor is how much other groups want to be your friend. It seems clear that majority groups will befriend Jews more easily than blacks. Bottom line: Jews are more cliquish than blacks.