[jmherbener]

Needless to say, a paper purporting to show that demand curves slope upward to the right has been controversial.

Here’s are a few answers to Card and Krueger:

http://mises.org/daily/2596/Minimum-Wage-Laws-Economics-versus-Ideology

http://mises.org/daily/6638/Welfare-Minimum-Wages-and-Unemployment

https://mises.org/daily/2130

Here’s a piece claiming that Krueger himself disavowed the conclusion you cite:

http://www.forbes.com/sites/susanadams/2011/08/31/obama-nominee-pulled-back-on-minimum-wage-defense/