The company partly blames the shortfall on its own hiring strategy. Its focus was on hiring women as senior engineers, which takes longer than standard-level workers. Pinterest is addressing this in part through expanding its use of a "Rooney Rule" (where it interviews at least one woman and one person from an underrepresented group) for recruitment beyond executive positions.

This isn't to say that Pinterest fell short across the board. It easily hit its goals for adding people from underrepresented groups, including both engineers (now at 9 percent) and everyone else (12 percent). However, the figures make clear that diversity in tech is difficult, and isn't simply a matter of setting targets and waiting for a broader demographic to walk through the door. Candidates have to get an opportunity to prove themselves, as Pinterest notes. Also, there's the matter of fostering greater interest in the first place. Tech giants are taking steps to encourage women to code after decades of discouragement, but these efforts might not bear fruit for years.