The article fails to address the field in which the degree is issued -- some PhD degrees do much better than others. Here's an article that lists the ten best, and ten worst, degrees to acquire in terms of career success and income:

http://content.time.com/time/specials/packages/completelist/...

The top of the best degree list? "Mining and Mineral Engineering"

The bottom of the worst degree list? "Counseling and Psychology"