Tuesday, September 6

Which is denser: New York or Los Angeles?

Your intuitions are correct. New Yorkers live in neighborhoods with much higher density than do Angelenos. But its not obvious how this conclusion is reached, and there's plenty of confusion going around about measuring density. Where you draw the lines on the map can have a significant impact on the results you get.

If you measure density purely regionally, Los Angeles comes out ahead. I've used the Census Bureau's MSA to show the two metro area's population densities in 2010. Sometimes the geography of Urbanized Area is used to capture the region, but that hasn't been determined for 2010 yet. So the MSA will do ...

However, this measurement misses the important story. As Ryan Avent explains,
"Simple population density measures the average density across a particular area. If you have a metro that covers a large area but which features a very dense core, however, you can easily have a situation in which the vast majority of the metro’s population lives at densities above the average population density. I think it’s more informative to focus on weighted-average population density."
  So here's the weighted-average density (by census tract) for the two metro areas:

New York metro goes from being about 30% behind LA in regional density to more than doubling LA in average neighborhood density.

If you were to drop from a parachute flying over the center of a city on a very windy day, the first regional density figure would tell you how many people to expect to see in the square mile around the random place in the region you land. However, if you currently live in the New York or Los Angeles metro areas (or are considering moving there), the latter figure would tell you how many people you would expect to see in the square mile around you. It's tethered to actual human experience, which is usually what we are asking about when we talk about density.


Laurence Aurbach said...

Daniel, you are comparing different units in the example above. You are comparing the New York consolidated metro area with the Los Angeles primary statistical area. A consolidated metro area consists of several primary metro areas bundled together.

If you compare primary metro areas with each other, you'll find that New York is several times more dense than Los Angeles. Similarly, if you compare consolidated areas with each other, you'll find that New York is much denser.

Daniel Nairn said...

It's hard to tell on the map here, but this actually is the primary MSA for New York. The Consolidated MSA goes into Connecticut and is a fair amount larger.

Laurence Aurbach said...

You're right, I stand corrected! What I said was true for the 2000 Census, but the MSA boundaries have been changed since then.

Still, comparisons that use other Census units show that density statistics depend largely on where one draws the boundaries:

New York Combined Statistical Area: 1,877 persons/square mile
Los Angeles Combined Statistical Area: 525 persons/square mile

New York Metropolitan Division: 7,301 persons/square mile
Los Angeles Metropolitan Division: 2,066 persons/square mile

(Based on 2009 population estimates and current Census boundaries.)

Laurence Aurbach said...

Correction: The density of the Los Angeles Metropolitan Division is 2,418 persons/square mile.

Nathan Landau said...

The regionwide density gives you a measure of land consumption, or land preservation, if you will. The denser an urbanized area is at the overall regional level, the less land it will consume for a given population.

But the average density by census tract tells you what the lived urban experience will be, how it will feel, what kind of services it can support etc. Metro New York is extremely dense at the core but very spread out at the edge of the region, metro Los Angeles is much less dense at the core but has far fewer really low density areas.

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