Bloomberg BNA reports:

How often does a unit of already-unionized workers actually decide to formally say goodbye to their union—and is it happening more often now than in the past?

Actually, it is happening less often. The (National Labor Relations Board) reported 228 decert elections in 2012—the lowest total since we started tracking NLRB election data in the mid-1980s. Unions typically faced more than 400 decert elections a decade ago. Even as recently as 2007, 331 decert attempts made it to the election phase.

But that doesn’t necessarily mean that unions are doing a better job of hanging on to their members nowadays. Of those 228 elections last year, unions won only 87 — by far the lowest total on record — earning a 38.2 percent win rate that itself marks a five-year low. In terms of living, breathing members, the 2012 figures were similarly bleak for unions. Of the 14,051 workers in bargaining units threatened with decertification, only about half — 7,326 — remained unionized after the votes were counted, marking the lowest retention total on record.

Among individual unions, one organization accounted for more than one-fifth of all decert elections in 2012. The Teamsters were besieged with 51 decerts, far below its yearly average but far above the total for any other union. The union was shown the door in 38 of those elections, for a 25.5 percent win rate. The Teamsters were able to hang on to only 743 of the 2,256 workers eligible to vote in the elections.