NEW YORK — The percentage of US workers in labor unions took an unusually large fall in 2012, dropping to 11.3 percent last year from 11.8 percent in 2011, the Bureau of Labor Statistics announced Wednesday.

The total number of union members also took an unusually big drop, by 400,000, to 14.366 million, even though overall US employment rose by 2.4 million last year, the bureau said. From 2010 to 2011, the number grew by 50,000, and the percent unionized fell only 0.1 percentage point.