Population Size & Income

Visualizing population size and median household income in all 3,000+ U.S. counties

The 2012 - 2016 American Community Survey, is a massive five-year study conducted by the U.S. Census Bureau.

Recently I dug up some data from this study to analyze two factors: county population size and median household income. I wanted to know if there was any relationship between the population size of a county and the corresponding median household income in that particular county.

It turns out that the correlation between county size and median household income is 0.24, which indicates that there is a positive relationship between county size and income. Larger counties tend to have higher incomes and smaller counties tend to have lower incomes.

To see just how this relationship plays out around the country, check out the scatterplot and corresponding map below. In the scatterplot, each dot represents a county. Population is along the x-axis (on a log scale) and median household income is along the y-axis.

Hover over individual circles to see the county names. Click and drag a box anywhere you'd like in the scatterplot to see the corresponding counties highlighted in the map below.

Note: These interactive visualizations will work on mobile, but are best viewed on desktop.

Four County Sizes

One way to analyze this data is to group the counties into four equal quartiles based on their size. The table below shows the average median household income for counties based on their population size:

County Size (population) Median Household Income
Greater than 68,000 $56,270
25,751 - 68,000 $46,662
11,000 - 25,750 $43,729
Less than 11,000 $45,265

The Ten Largest Counties

The table below shows the ten largest counties by population, along with their median household income.

County Population Median Household Income
Los Angeles County, California 10,057,155 $57,952
Cook County, Illinois 5,227,575 $56,902
Harris County, Texas 4,434,257 $55,584
Maricopa County, Arizona 4,088,549 $55,676
San Diego County, California 3,253,356 $66,529
Orange County, California 3,132,211 $78,145
Miami-Dade County, Florida 2,664,418 $44,224
Kings County, New York 2,606,852 $50,640
Dallas County, Texas 2,513,054 $51,411
Riverside County, California 2,323,892 $57,972

The Ten Smallest Counties

The table below shows the ten smallest counties by population, along with their median household income.

County Population Median Household Income
Loving County, Texas 76 $56,875
Kalawao County, Hawaii 91 $65,625
King County, Texas 274 $57,083
McPherson County, Nebraska 425 $53,750
Arthur County, Nebraska 437 $40,375
Petroleum County, Montana 445 $38,250
Loup County, Nebraska 542 $56,750
San Juan County, Colorado 552 $41,250
Kenedy County, Texas 558 $24,000
Harding County, New Mexico 565 $32,404

Explore the Data

It's amazing to see just how much household income and population size vary from county to county. Median household incomes ranges from $18k up to $125k and population size ranges from 76 in Loving County to over 10 million in Los Angeles County, California.

Feel free to explore the data further yourself by using the scatterplot to filter the map. Both the scatterplot and the map are interactive, so hovering over individual circles or individual counties will reveal county name, population size, and median household income for that particular county.

Technical Notes: I downloaded data for these visuals directly from the U.S. Census American FactFinder. I used D3.js, a JavaScript visualization library, to create the map and scatterplot. The idea for this article was inspired by this block from Chris Given.