In 1987, fewer than 18 percent of wives earned more than their husbands. by 2013, that proportion had grown to approximately what percentage?

Niall McCarthy posted an article in Forbes (dot) com about the percentage of wives earnings as to their husband. He stated that according to the Bureau of Labor Statistics, in the year 2013, 29.3% of wives earned more than their husbands. This data is taken from families that both wife and husband earn. There is a significant increase of 62.78% from 18% in the year 1987.