Sam Peltzman is a legendary University of Chicago economist. I first encountered his research during high-school debate, where his work was being quoted for one counter-intuitive proposition after another. Most famous, perhaps, is his suggestion that mandatory seat belt laws wouldn’t reduce deaths—at least certainly not as much as forecast—because drivers would compensate for their “forced” safety consumption by driving faster. This is known as the Peltzman Effect. (As to the empirical validity of the claim itself, see this recent post by Steve Levitt on his Freakonomics blog.)
We look like we are getting to run another test of the Peltzman Effect as Wal-Mart and environmentalists (together!) (NYT, 1/2/07 $) push us towards compact fluorescent light bulbs (CFLs). Will CFLs save energy as consumers swap 60-watt incandescents—Thomas Edison’s light bulb—for 15 watt CFLs? Or will consumers seize the day(light) by swapping 60-watt CFLs for 60-watt incandescents? If so, that will offset projected energy savings (and the corresponding carbon dioxide reductions).
We should back up a bit. The common measure for light is watts, so we speak of 60-watt light bulbs and 100-watt light bulbs. But this turns out to be a bizarre way to talk about light: watts measure the amount of power used—the input—when what we actually care about is the amount of light created (the output, measured directly in lumens).
CFLs produce light using less power. Environmental Defense notes that CFLs produce roughly the same light as ordinary bulbs with one-quarter of the power used and they are currently running a campaign to get consumers to pledge to swap 1 million ordinary bulbs for CFLs. They are at roughly 200,000 bulbs pledged and forecast more than 200 million pounds of avoided carbon dioxide.
But that assumes that consumers just want to reproduce the light that they have. My guess is that that is unlikely. If your house is like my house, you max out your light fixtures. If the fixture holds a 100-watt bulb, you put one in; you don’t stick in a 60-watt bulb.
Now we get to the key point, which I assume to be correct, but if I am wrong, please let me know. I assume that the watts ratings on a lamp are designed to address the potential heat that the lamp can withstand. If so, we should be able to replace a 60-watt ordinary bulb with a 60-watt CFL. As a practical matter, there clearly will be size issues, but if most of us are currently maxing out our fixtures, many consumers may find it attractive to upgrade their light when they switch to CFLs, and that will undercut the likely power and pollution savings promised for CFLs.
So fluorescents and Sam Peltzman are joined again. I say again, for if you were a University of Chicago undergraduate, as I was, you know that Sam has always dressed in way that can only be described as fluorescent (indeed, you might describe Sam himself as a compact fluorescent).