The tape was released shortly after the U.S. Defense Intelligence Agency had raised the military terror threat level from "significant" to "high, " its top level, as authorities braced for a possible terrorist attack.

CNN: Al-Jazeera airs purported al Qaeda message

Slaughter has found a statistically significant relationship between declining unionization and increasing foreign investment across industries in the U.S. Firm-level analysis by Bruce Fallick of the Federal Reserve Board and our colleague Kevin Hassett also finds a negative relationship between unionization and investment.

FORBES: How To Lure Foreign Investment To The U.S.