The U.S. labor movement may be on the verge of massive growth, according to Dan Clawson. He argues that unions don't grow slowly and incrementally, but rather in bursts. Even if the AFL-CIO could organize twice as many members per year as it now does, it would take thirty years to return to the levels of union membership that existed when Ronald Reagan was elected president. In contrast, labor membership more than quadrupled in the years from 1934...