Dr. Ng is puzzled by some findings in the literature. She read that one of the proposed explanations in the standard cross-section regressions for why married men earn more than single men is that: "Marriage has a positive effect on workers' productivity. The question remainswhether married men are more productive because they are married, or whether men who do better on the 'Marriage market' tend to also do better on 'Job market.''

(i have the raw data of 100 NBA players of their marriage, wages, age, race - black/non-black, productivity. I am not sure how to do the questions analysis of my data...)