You view Cato as an unbiased source in this issue?
All sources are biased in one way or another. Having said that, the numbers speak for themselves. Any think tank that supports the free market seems to be more open and honest than let's say the AFL-CIO "think" tank.
Try the Heritage Foundation too - lots of important info there.
http://www.heritage.org/Research/TradeandForeignAid/hl872.cfm