The curse of CSI

This line from the latest Case-Shiller house price report caught my eye:

Las Vegas and Miami share the dubious title of the weakest markets in January, reporting double-digit annual declines of 19.3%.

Now, what do Las Vegas and Miami have in common? Yup, they are locations for two of the three CSI franchises.
Even if we allow for the fact that prices in the third CSI area - New York - are holding up relatively well, the CSI effect seems big. Prices in the three CSI cities have fallen by an average of 14.8% in the last 12 months, compared to an average fall of 8.7% in the other 17 metropolitan areas covered by the Case-Shiller indices.
Coincidence? No. There's an obvious reason for this - the salience effect. CSI causes people to exaggerate the extent of violent crime in its cities, causing people, at the margin, to avoid them.
Granted,  the CSI effect doesn't seem significant in conventional statistical terms. Regressing annual price changes upon a CSI dummy (1 for Las Vegas, Miami and New York and zero for the other 17 cities) yields a p-value of 15.1%, against the null hypothesis of a zero effect. But remember:
1. Why should we be classical statisticians about this? If your Bayesian prior is that there is a CSI effect - as theory predicts - the evidence provides some corroboration.
2. Don't confuse statistical and economic (in)significance. As we've seen, the effect is economically significant - worth over $15,000 for a house priced at $250,000 this time last year.
3. CSI is not the only show affecting perceptions of crime and therefore prices. If we add a Numb3rs effect (giving LA a dummy value of 1 as well), then the p-value for a combined CSI+Numb3rs effect drops to 5.9% - significant at the 10% level, as they say. Papers have been published with less.
Pedants will moan that this is just a nonsensical excuse to carry a picture of Emily Procter. But what do they know?

Comments

[Nylund]

If Baltimore was on the list, you'd have to add the Wire. It might be close enough to DC. Or, you could count "The Shield" for DC. Count movies and "The Departed", "Gone Baby Gone" "etc. could all affect Boston.

PS. I teach stats at my university and today I cover linear regressions. What a coincidence.

[Matthew]

You really have to take into account their start dates - 2000 for las vegas, 2004 for new york, not sure about the others. Think this might scupper the idea totally - didn't las vegas house prices rise until recently?

[Shortshire]

Nylund, "The Shield" is based out of California instead of DC.

[Planeshift]

Would this mean that there is an externality of consumer demand for crime dramas? Should we therefore impose a tax on popular crime dramas to compensate the victims?

[a very public sociologist]

I certainly agree with you Nylund. You can pick up a vacant featured in the series for as little as $100!

[chris]

Matthew - the start dates don't scupper the theory, but just make it hard to test. The thing is, the effect of CSI on crime perceptions would be non-linear. The first episode will have had a negligible effect, but the cumulative effect of 8 series could well be large. Maybe it's only in the last few months that a tipping point was reached.

[ChrisP]

"Pedants will moan that this is just a nonsensical excuse to carry a picture of Emily Procter" Actually I was wondering about the sharp increase in full-bosomed women illustrating these blogs. Now I'm told that isn't purely gratuitous I'm working hard to discover a reason. Worse: I worry that when CD goes to the rural wastelands we'll have sheep as illustrations. If so, don't go!

[Mark Wadsworth]

Aha! CSI stands for Case-Schiller Index. THe penny has dropped.

[Ken Houghton]

Gratuitous pictures of Ainsley Hayes are always welcome and understood, even ones that appear slightly washed out. (To be clear, I don't object to the Gratuitous Sarah Harding pictures either, but can't tell her from Tonya Harding; was Girls Aloud the UK version of Menudo?)