Embarrassment by variable.

April 2, 2010, 8:38 am

From Nate Silver, a social scientific lapse.

A study purporting to find a connection between stimulus spending and the partisanship of a district suffers from an obvious flaw. But in so doing, it provides an example of why it’s important to retain some common sense — and some sense of context — when conducting a statistical analysis.

The study, by Veronique de Rugy of George Mason University and the National Review, claims that congressional districts which elected a Democrat to the Congress received a larger amount of stimulus finds by a margin which is statistically significant even after controlling for certain other effects like the unemployment rate. However, the study does not control for at least one other variable that is overwhelmingly important in determining the dispensation of stimulus funds.

The variable in question is in fact pretty obvious if you simply look at the districts that have received the largest amount of stimulus money, according to de Rugy’s dataset.

The district that received the largest amount of stimulus funding in the 4th Quarter of 2009, according to de Rugy’s tally, is California’s 5th Congressional District. Is there anything notable about the 5th Congressional? Well, it is home to the state capital, Sacramento. Let’s keep that in mind.

Next on the list is New York’s 21st Congressional District. The largest city in the 21st is the state capital of New York, Albany.

Third is the 21st Congressional District of Texas. It contains parts of Texas’ state capital, the wonderful city of Austin. (Another district that contains parts of Austin — the 25th — ranks 14th on de Rugy’s list.)

At this point, it ought to be pretty obvious what is going on. The three districts receiving the largest amount of stimulus funds are home to the capitals of the three largest states — New York, California, and Texas. Let’s pause for a moment and make a bold prediction. I’ll bet you that the district that ranks 4th on the list will contain the capital of the 4th largest state, Florida.

Bingo. Up 4th on the list is Florida’s 2nd Congressional, home to Tallahassee.

Fifth is Pennsylvania’s 17th, which hosts the state capital, Harrisburg.

The sixth through tenth districts contain the capital cities of other large states: Ohio, Georgia, Michigan, Illinois and New Jersey, respectively. They are followed by districts that include the state capitals of Indiana, Tennessee, Virginia — then another part of Austin, Texas — then Arizona, Missouri, North Carolina and Wisconsin. Finally, in 19th place is South Carolina’s 3rd Congressional District, which does not host a state capital. (Ironically, it has elected a Republican — J. Gresham Barrett — to the Congress).

This, of course, makes perfect sense. A lot of stimulus funds are distributed to state agencies, which are then responsible for allocating and administering the funds to the presumed benefit of citizens throughout the state. These state agencies, of course, are usually located in or near the state capital.

Something similar occurs with scholars who get hot under the collar over the distribution of New Deal construction funds to the West and South. It’s politics! Because the western states were swing states, and the southern states were loyal Democratic states! Or perhaps it was because the West and the South were the parts of the country that most needed infrastructure spending and that would benefit most from it, and it was much cheaper to build in western states where the federal government already owned the land anyway.

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