Unintended Consequences Everywhere

One thing I always like to consider when I look at a proposed policy, law, etc, is the law of unintended consequences, which is of particular importance to economists, because of Mankiw's 4th Principal of Economics: people respond to incentives.

And so it is completely surprising that Stephen Dubner over at the Freakonomics blog has apparently forgotten the law:

Sometimes a good idea is so obvious that you can't believe no one has made it happen yet. That would seem to be the case with something called the Impair Aware Alcohol Level Indication System. It's a machine you can put in a bar or restaurant that lets you measure your blood alcohol level so you know if you're fit to drive or not.

I'm not sure which surprises me more, the fact that Mr. Dubner thinks this idea is new (they tried this in Wisconsin when I went to college in the early 90s!), or the fact that Mr. Dubner, as an amateur economist, thinks the idea is good -- i.e. that he didn't think of the most obvious unintended consequence of the IAALIS, which is the very consequence that caused Wisconsin to stop using it almost immediately and that the first commenter at the above blog entry vividly describes:

We tried something similar once when I was an undergraduate in a fraternity. We bought a breathalyzer machine so we could ascertain whether or not someone was too drunk to drive home. Good in theory, but it quickly turned into "see who can blow the highest," which quickly turned into "wake him up so he can take the breathalyzer. I bet it'll be a new record!"

I think, as unintended consequences come and go, this one was easy to spot from miles away.