Trade and Wage Insurance

Interesting story in today's Washington Post about wage insurance. "The nation's existing wage-insurance benefit was tucked into the federal Trade Adjustment Assistance program in 2002. It applies only to manufacturing workers 50 and older who are laid off as a direct result of international trade. They are eligible if they take a new job within six months of the layoff that pays less than $50,000 a year. The program, administered by the Labor Department, will make up half of a worker's lost wages for two years, up to $10,000."

One puzzle, though--why do many labor unions oppose such measures?