(September 2012) There is a growing gap in the United States between the haves and the have-nots. The Gini Index, which measures inequality across households, registered its first significant year-to-year increase since 1993, according to data released last week by the U.S. Census Bureau. Since 1967, household inequality has increased by 20 percent.1 But levels and trends in inequality depend on where you live, with the highest Gini coefficients in California and parts of the Northeast and South, and lower levels of inequality in states in the Midwest and Mountain West.

The Gini Index measures the dispersion of income across households. A value of "0" represents an equal distribution of income, while a value of "1" represents perfect inequality. In 2011, the national Gini Index stood at .477, up from .470 in 2010.2 Another measure of inequality, based on the share of income received by the top-20 percent of households, shows a similar increase. In 2011, the top-20 percent of households controlled over half (51 percent) of all household income. 

New data from the 2011 American Community Survey can be used to look at state and local-level patterns of inequality.3

In 2011, there were just 10 states with a Gini Index higher than the national average: California, Connecticut, Florida, Georgia, Louisiana, Massachusetts, New Mexico, New York, Tennessee, and Texas.4 Many of the states with high levels of inequality also have large, diverse populations and high levels of residential segregation. Among the states, income inequality was highest in New York, where the top-20 percent of households controlled 53 percent of household income. States with the lowest levels of inequality included Alaska, Hawaii, Utah, Vermont, and Wyoming.5

Income inequality increased significantly in 20 states between 2010 and 2011. States with the largest increases in inequality include Maine, Nebraska, New Mexico, and West Virginia. The reasons why inequality increased in these states are unclear, but inequality is rising rapidly in more densely populated metropolitan areas within these states. In West Virginia, there was a sharp increase in the Gini Index in Berkeley County—a suburb of the Washington-Baltimore Metropolitan Area and the fastest-growing county in the state during the past decade—from .397 to .484. In Maine, inequality was up sharply in Cumberland County, the most-populous and affluent county in the state. And in Nebraska, inequality increased from .461 to .484 in Douglas County, where Omaha is located. These results suggest that the recent increase in inequality may be tied to growing income disparities—and uneven economic recoveries—in large cities and their suburbs.

The table below shows the 20 counties with the largest increases in income inequality between 2010 and 2011. More detailed data for states, large cities and counties, and metropolitan areas are available in PRB's DataFinder.


Counties With the Largest Increases in Household Income Inequality, 2010-2011
(Among Counties With at Least 65,000 People)

  Gini Index  
Name 2010 2011 Change
Berkeley County, West Virginia 0.397 0.484 0.087
Twin Falls County, Idaho 0.375 0.455 0.080
Calhoun County, Michigan 0.415 0.493 0.078
Shiawassee County, Michigan 0.378 0.454 0.076
York County, South Carolina 0.416 0.491 0.075
Citrus County, Florida 0.414 0.489 0.075
Charlotte County, Florida 0.420 0.493 0.073
Delaware County, Indiana 0.442 0.515 0.073
Indian River County, Florida 0.470 0.540 0.070
Robertson County, Tennessee 0.346 0.416 0.070
Clark County, Indiana 0.389 0.456 0.067
Forrest County, Mississippi 0.490 0.554 0.064
Wicomico County, Maryland 0.444 0.506 0.062
Walker County, Georgia 0.416 0.477 0.061
Newton County, Georgia 0.399 0.459 0.060
Warren County, Kentucky 0.487 0.546 0.059
Pickens County, South Carolina 0.427 0.486 0.059
Lafayette Parish, Louisiana 0.460 0.517 0.057
Tompkins County, New York 0.452 0.508 0.056
San Patricio County, Texas 0.429 0.483 0.054

Note: Estimates are subject to both sampling and nonsampling error.
Source: U.S. Census Bureau, American Community Survey.


Mark Mather is associate vice president of Domestic Programs at the Population Reference Bureau.


References

  1. U.S. Census Bureau, "Table H-4. Gini Ratios for Households, by Race and Hispanic Orign of Householder: 1967 to 2011," accessed on Sept. 17, 2012.
  2. Carmen DeNavas-Walt, Bernadette D. Proctor, and Jessica C. Smith, U.S. Census Bureau, "Income, Poverty, and Health Insurance Coverage in the United States: 2011,"Current Population Reports, P60-243 (2012).
  3. Data are available for geographic areas with populations of 65,000 or more.
  4. Each of these states had indices higher than .475, which is the national Gini Index based on 2011 American Community Survey data. The Gini Index in the District of Columbia was .534.
  5. U.S. Census Bureau, "Household Income for States: 2010  and 2011," accessed on Sept. 20, 2012.