“The safer they make the cars, the more risks the driver is willing to take. It’s called the Peltzman effect.” — Some CSI Episode

The basic idea is so simple that it’s hardly controversial.  If you reduce the cost of doing something, you would expect more of it.  The classic Sam Peltzman paper has to do with making cars safer, which reduces the costs (in terms of potential injury or fatality) and hence increases “driver intensity,” as Peltzman puts it.  The startling result is that the behavioral changes completely offset the technological improvements, though this does not have to be so.

This is similar to the “rebound effect,” where improving energy efficiency or fuel economy, for example, causes people to set their thermostats more aggressively or to drive more miles (that is, because the marginal costs go down).

The Peltzman effect has crept into my RSS feed twice in the past week.  From this morning’s Marginal Revolution:

The NHTSA had volunteers drive a test track in cars with automatic lane departure correction, and then interviewed the drivers for their impressions. Although the report does not describe the undoubted look of horror on the examiner’s face while interviewing one female, 20-something subject, it does relay the gist of her comments.

After she praised the ability of the car to self-correct when she drifted from her lane, she noted that she would love to have this feature in her own car. Then, after a night of drinking in the city, she would not have to sleep at a friend’s house before returning to her rural home.

Well, that certainly makes me feel safer.

One of the classic jokes associated with the Peltzman effect is that NHTSA should put a spear extending out of the steering column, making the driver exercise extra caution so as not to be impaled. In that vein, the good folks at Organizations & Markets alerted me to this cartoon:

Pretty funny.

Peltzman is one of the most prominent empirical economists ever.  Certainly, having an “effect” named after you is a pretty big deal.  Some of the more astute of you also recall Peltzman from the Stigler-Peltzman capture theory. Love him or hate him, he is an interesting character.  I recommend this interview at EconTalk.