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.  

MOCO Map of the Week--Percent Black/African American by Census Tract, 2010

Today's map looks at the distribution of Montgomery County's Black/African American population by census tract.

People who identify as Black or African American comprise 16.62% of MOCO's population.  Their share in MOCO is lower than it is for the state (29.4%), but higher than it is in the country as a whole (12.6%).

A few spatial patterns stand out on today's map.  First, the Black/African American population is spatially clustered in two places in the county--Gaithersburg/Montgomery Village and along the border with Prince George's County.  Second, the top 5 census tracts with the highest percentages of Black/African American residents are all located on the eastern edge of the county (either bordering the county, or bordering a census tract that does). Finally, the county's Black/African American population is largely concentrated outside the beltway, despite a significant cluster along the northeastern border of DC.

Next map will look at statistically significant clusters of the Black/African American population.  Stay tuned! 

Map notes:  The data for this map is from the 2010 census.  The census does not disaggregate between people who identify as African American and those who identify as Black (usually, though not always people from other countries with African heritage).