They protest too much...

Megan McArdle:

"What I said is, the studies so far done often cannot exclude the possibility that there is no effect--this is true of one of the two studies that IOM/Urban relied upon, and also of the largest observational study done to date, which found no effect. That is not the same as saying there is no effect. Health data, like economic data, is very noisy. Sometimes effects that we're pretty sure exist just can't be easily teased out of the data . . . like, oh, I dunno, the effectiveness of fiscal stimulus, say.

What I am saying is that we don't know how big the effect is. Refuting me involves, not saying that well, here's another study showing some effect, but rather, taking a stand and saying we do know how big the effect is, or at minimum, that we can prove it's probably at least 20,000 people a year, the figure I was discussing."