Roberts notes the responses from Cowan and Caplan-see here-and also notes an email he received which suggested suggests Time on the Cross, Fogel and Engerman's study of slavery. Roberts then goes on to say,
Most or all of these observations miss the point, or at least the point I was trying to make.As to establishing truth or results that are reliable, I argued before that the thing to keep in mind is that a single result or paper will not settle a question. But a series of results giving the same answer to the same question involving different data sets, different time periods, different countries, different approaches to answering the question etc will do so. I think what convinces people as the rightness of a result in the accumulation of evidence in its favour. This evidence may or may not involve the kind of sophisticated empirical work Roberts is referring to.
Empirical work is very important.
A careful study of the facts can have tremendous influence.
Sophisticated regression analysis can narrow our guesses as to magnitudes. But I don't think we need fancy regression to conclude that people aren't always rational. Or that police can reduce crime. Or to look at the nature of resale price maintenance. On the stuff where people have priors and bias—such as the dynamic impact of taxes on revenue—I don't think the empirical evidence is very convincing of the skeptic.
I understand that science moves slowly and that people at the margin are who eventually count.
But I really don't think the empirical record of sophisticated empirical work is very impressive. In fact, I think I could make a case that sophisticated empirical work is most productive for publishing papers and less productive at establishing truth or useful findings that are reliable.