We often see headlines about the most expensive cities in America, where writers look at the average or median price for renting. But by zeroing in on a single number, those reports doesn’t always paint a complete picture of affordability.

Graphic by the author. Click for an interactive version.

I developed an interactive graph where users can explore how many people are living in neighborhoods (in the graph above, I looked at ZIP codes) of differing prices.

Measuring a city’s rent with the median — the middle number in a series of numbers — is useful for quick comparisons. But in only using one number, we lose valuable information about affordability because we ignore the variation in prices.

While the median rent for the entire DC census-designated urban area is about $1500, some areas are cheaper (the 20010 ZIP code, containing northern Columbia Heights and Mount Pleasant sits around $1250) and others are more expensive (20016, the Palisades, is at $1800).

In the interactive graph, the X axis measures rent and the Y axis measures the percent of the city’s population living in a ZIP code where the median rent is less than X. For example, in the chart above, we see that 60.5% of Houstonians live in a ZIP code where the median monthly rent is no more than $999. The further a city’s series is to the right, the more expensive it is.​ You can read more about the technical details here.

According to this data, DC is one of the most expensive urban areas in the US. (This is consistent with the area-wide median rent figure, which is higher than that of most cities.) There’s a clear shortage of affordable areas: only about 6% of DC-area residents live in a ZIP code where median rent is less than $1000. That’s slightly worse than other expensive places, like the Bay Area (7%) and NYC (9%), and considerably worse than more affordable cities, like Chicago (57%).

What do you notice in these graphs?