Ethnic differentiation by blocks within census tracts

How common is ethnic differentiation within census tracts and what types of tracts are most likely to exhibit this tendency? This research attempts to answer these questions with block data from the 1990 U.S. census for Los Angeles County. We measured non-random unevenness in ethnic percentage within tracts for twelve ethnic populations by means of an adjusted index of dissimilarity. Of the total of 300 sampled tracts, 48% showed statistically significant differentiation at the block level. Census tracts frequently mask details of ethnic patterning, especially in transition zones between larger ethnic settlement regions. Ethnic differentiation was most clearly related to block variations in housing type and cost, and tracts with fairly uniform housing were much less likely to show significant internal differentiation. Block-level differentiation was no greater for blacks than for some Asian groups and was average or low for non-Hispanic whites and people of Mexican-origin.