MOCO Map of the Week--Ethnic Clustering Part 2

Today's map is a slight variation on my last map, which showed the spatial distribution of the county's Black/African American population.  Today's map is a standard deviation map.  This means that each tract is categorized based on where the Black/African American share of the population fits in the wider distribution (i.e. within one standard deviation of the mean, within two standard deviations, etc.).


A bit on measurement:  In the tracts outlined in black the Black/African American share of the population that is greater than 2 standard deviations from the mean share.  The mean share of the Black/African American population is 16.62%.  The standard deviation is 13.58%.  Tracts outlined in black have a Black/African American share of the population that is greater than 43.78% (i.e. the mean + 2 standard deviations).  

So, what are the notable patterns here?  Unlike the earlier standard deviation maps I produced for the Asian and Hispanic populations (you can see them here), there are not multiple clusters.  Instead, all of the tracts with a statistically significant share of the Black/African American population are near one another and located on the eastern edge of the county.  In many ways the eastern orientation is not surprising given that Blacks/African Americans comprise a majority of the population in neighboring Prince George's County.