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.