To understand the extent of income segregation in New Jersey, we have used the same methods we employed to analyze racial and ethnic segregation. This means that we must first understand how diverse New Jersey’s counties are. Just as in that method, we have used data from the U.S. Census Bureau’s American Community Survey, only instead of race or ethnicity of individuals, this time we are analyzing the diversity of household income in each county. In this exercise, we used the 10 mutually exclusive income “buckets” or deciles provided by the American Community Survey. In this instance, the Diversity Index would tell us how evenly distributed household income is in a particular county. The higher a county’s Household Income Diversity Index, the more likely it is that similar shares of county households fall into every income group. If household income in a county were evenly distributed among all ten income groups, exactly 10% of all households would fall into each household income group. The resulting Household Income Diversity Index of a county in this scenario of total income diversity would be 100.00. To review how we calculated the diversity index of counties, please see our previous posts regarding racial and ethnic diversity.
Map 1 shows how household income diversity plays out across counties in New Jersey. Counties are shaded based on how their Household Income Diversity Index score compares with all other US counties. Counties whose Diversity Index score falls in the bottom quartile (25%) of all US counties are shaded in yellow, while counties whose Diversity Index score falls in the top quartile of US counties are shaded in dark blue.
Map 1: Household Income Diversity in NJ Counties 2010-2014
For another view of how Household Income Diversity Index scores of individual New Jersey counties compare to the quartiles of all US Counties, see Chart 1.
Looking at the chart above, we can see how far particular New Jersey counties rise above or fall below national quartiles of household income diversity. We can also see that Essex County is, in fact, the most diverse county in the US in terms of household income (i.e. has the highest Household Income Diversity Index score of any US county). While it doesn’t have a perfect score of 100.00, its score of 89.30 means that households in Essex County are more evenly split among the ten income groups than any other county in the US. We also see that that 12 of New Jersey’s 21 counties have Household Income Diversity Index scores that fall in the top quartile of US Counties and can be considered more diverse in terms of household income. This equates to 57% of New Jersey’s Counties being considered more diverse, ranking it seventh out of all states, including the District of Colombia, as seen below in Table 1.
Yet another way to understand if New Jersey’s counties are diverse, in terms of household income, is shown in Table 2. In this table, we can see that not only does Essex County have the highest Household Income Diversity Index score of any US county, but three New Jersey counties fall in the top 10 highest ranked US counties. No other state has more than one county in the top ten.
This evidence not only suggests that New Jersey counties are very diverse, in terms of household income, but also proves that New Jersey counties are some of the most diverse in the US. However, this tells us nothing in regard to how household income is physically distributed throughout a county. Check in next week as we explore the distribution of household income within individual New Jersey neighborhoods to see if neighborhoods are as diverse as the counties they lie within, or if pockets of similar incomes are seen throughout counties. For now, look at Table 3, below, to see how each New Jersey county compares in terms of its Household Income Diversity.
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Author: John Manieri, AICP
Research, Analysis, and Technical Assistance: Chanel Donaldson, Dineth Correia