The unexplained difference, the economists say, may be due to discrimination in hiring and raises. Discrimination is hard to put a finger on. But in this case it seems to fall under the Sherlock Holmes rule: When all the other possible explanations have been eliminated, the remaining explanation, no matter how unlikely, is the truth. They do note experiments done with real employers showing that, for certain jobs at certain businesses, women were less likely to be interviewed than men. But they end on an optimistic note -- for women, at least.