Women made up 15 percent of those employed in software programming and other computer jobs in the 1970s, rising to 34 percent in 1990, according to the Census Bureau. But since then, in spite of two big booms, women’s share of computing jobs has fallen to 27 percent. That decline stands in contrast to the gains women have made in other fields like life and physical sciences and mathematics where they are approaching parity with men in total numbers, though they still lag in leadership roles.

Technology boardrooms seem curiously hidebound in other ways. Twitter’s board, for instance, is dominated by technology specialists, even though it is a media company that derives much of its value from people’s urges to broadcast their thoughts. It has just one media executive on its board, Peter Chernin, a former president of the News Corporation. And no director has political experience, even though world policy makers (the new Iranian president and the pope among them) use the service.

As to the shortage of women, some tech executives say there simply are not enough qualified women to go around. This seems to be little more than an excuse for inaction.