The US Census Bureau collects data and reports on the poverty level each year. Their statistical definition of poverty has to do with the affordability of food. As they describe, the Office of Management and Budget’s Directive 14 sets a money income threshold related to the after-tax spending by families on a food plan defined by the Department of Agriculture. At the time of this writing, the poverty income threshold for a family of four is $32,130.

The solid orange line in our FRED graph above shows the number of people, measured in millions, who lived in poverty between 1989 and 2023. In 2023, that number was estimated to be 40,763,043 persons. The dashed lines above and below the solid line show the boundaries (or range) of the 90% confidence interval associated with the poverty estimate.

Why does the Census provide a range for its poverty measure?

The Census Bureau estimates poverty rates using data from several different surveys. The regional sample size of the surveys impacts their reliability: In statistics, data obtained from small samples tend to be less reliable than data obtained from larger samples. The Census estimates take all this into account and include a 90% confidence interval for the reported figures.

What’s a 90% confidence interval?

In short, a confidence interval is the level of certainty about the accuracy of the estimate. The Census Bureau routinely employs a 90% confidence interval for its estimates. As they explain, a 90% confidence interval provides a level of certainty that, if you measure poverty using the same procedure multiple times, the estimated value will be within the range 90 out of 100 times.

How this graph was created: Search FRED for and select “90% Confidence Interval Upper Bound of Estimate of People of All Ages in Poverty for United States.” Click on the “Edit Graph” button and select the “Add Line” tab to search for “Estimate of People of All Ages in Poverty for United States.” Don’t forget to click on “Add data series.” Use the “Add Line” tab again to search for and add “90% Confidence Interval Lower Bound of Estimate of People of All Ages in Poverty for United States.” Lastly, use the “Format” tab to customize the line styles.

Suggested by Diego Mendez-Carbajo.