Gender, racial or ethnic discrimination:

1 Definitely explains all wage differentials between men and women, between whites and blacks, and between Jews and non-Jews.

2 Might explain some of wage differentials among groups, but because competition in hiring tends to reduce the extent to which employers can consider irrelevant preferences, probably not a large share of the differentials.

3 Definitely does not explain the wage differentials among groups because markets perfectly compete away the impact of all irrelevant preferences.

4 All of the above

5 None of the above