[bumxumer]

This has to do with the increase in Asian Americans in absolute and relative numbers among the population, I guess. Marriage outside the group rates should be corrected by the percentage of people there are inside the group to see how truly exogamous the minority or majority is.

For example, if all things were random and noone was endogamous, then in a city that was 5% Asian and 95% non-Asian you would find 95% of Asians married to non-Asians. You see numbers that are lower than that (let's say, 30% married to non-Asians). This shows how prevalent endogamy is. But to someone who hasn't studied population demographics, this seems very high, especially compared to the majority group (let's say non-Asians marry within their group 90% of times). A minority exogamy ratio will, all things constant, be higher than a majority due to simply this proportion effect.

Now when the minority's proportion in the population rises, then even if there's no change in the exogamy factor (culture or attitude), there will be an increase in endogamous marriages. If the city becomes 50% Asian and 50% non-Asian, then there will be more Asian partners available and, with the same endogenous exogamy ratio, there will be more endogamous marriages (let's say 75% Asians married with Asians and 25% Asians married with non-Asians).