Problems worthy of attack prove their worth by hitting back. —Piet Hein

Monday, 3 December 2012


I wrote a visualization of the populations of the largest cities in the US over the years. I got the idea when I was in Detroit in the summer, and read about the huge decline in Detroit's city population since the 1950s when the automotive industry was at its peak. According to Wikipedia's Shrinking cities in the USA page, Detroit has declined by 61.4% from its peak population. This is a decline of over 1 million, which makes it the largest decline among US cities in absolute numbers, but not in percentage terms since St. Louis has a slightly higher percentage decline (62.7%, or 537,502 people).

These figures are all for city populations, not for the greater urban or metropolitan areas, which, in the case of Detroit, have both significantly increased in size since the 1950s. Detroit has therefore seen one of the largest population shifts to the suburbs since the middle of the 20th century. Much has been written on the dramatic decline of Detroit's city population, and the impact on life there. These are some pieces that I found interesting:

How I wrote the visualization

I used the wonderful d3 library to write the visualization, combining elements of the Population Pyramid example with an updating bar chart. The documentation on Object Constancy was critical to getting the visualization to work.

The population data is from the US Census Bureau, although I found the actual files linked from Wikipedia's Largest cities in the United States by population by decade. I had to write some simple scripts to turn the source data into CSV files that d3 could read.


Tom Wheeler said...

This is a really cool visualization. I'd like to add some perspective on my fair city of St. Louis.

The population of the city has indeed declined, but this corresponds with an increase in the population of the metropolitan area (which currently has about 2.8 million people). Starting in the 1950s, the population of many cities started migrating to the suburbs. Most cities eventually annexed nearby areas, but the city limits in St. Louis have been fixed since about the time of the Civil War. St. Louis was pro-Union, but much of the state was under Confederate control at the time and this was an attempt by the city to stave off outside influence.

About ten years later, the City of St. Louis city seceded from St. Louis County, and this division has persisted in the Missouri constitution for more than 130 years! If the city and county were to ever merge, the combined population would be about 1.3 million people -- about 50% higher than the city's 1950 peak population.

Tom White said...

Thanks Tom, very interesting! The numbers and the visualization don't tell the whole story of course - they certainly don't illuminate the effects of city limits - so it's good to read more about it.