USA: female directors on company boards

The Corporate Library has published research exploring the proportion of women on the boards of companies in the Russell 3000 index. The report is available for download here (some personal information is required). The report notes (to quote from its executive summary):

Almost 90 percent of S&P 500 companies do have at least one woman on their boards, which accounts for the perception in some quarters that women’s representation is widespread. However, only 60 percent of companies comprising the Russell 3000 as a whole, and only half of Russell 2000 companies, have at least one female director".