Visualizing population density

MANHATTAN IS MORE EXTREME THAN YOU THINK IN POPULATION DENSITY

Slinging numbers around all day, one adage we believe is that most surprising statistics are wrong.

But here’s one that’s not: When you look at the 100 most populous counties in the USA, Manhattan (aka New York County) has about twice the population density of the next densest county (Brooklyn, aka Kings County), four times the density of the 5th densest county (San Francisco), and 13 times the density of the 10th densest county (Cook County, IL, home of Chicago).

Population density drops off sharply as you look at highly populated US counties, and New York City has 4 of the top 5. We color code by state in this graph:

The graph at the top of this post represents a square kilometer and draws a dot for every person in various counties. This representation is deceptive at high densities. It would look like a black square long before it got to 1,000,000 people (1,000 people by 1,000 people, each taking up a square meter). We just can’t show 1,000 by 1,000 dots on a graph that size.

We can be more faithful, and make things easier to imagine, if we talk about people per hectare.

But what’s a hectare? Glad you asked. It’s 100 meters by 100 meters. As we see below, it’s roughly one (US) football field by one football field:

Now the differences in densities are still dramatic, but it doesn’t look like people in Manhattan are packed in like sardines.

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