For years, blue-ribbon panels of experts have sounded the alarm about a looming shortage of scientists, mathematicians and engineers in the U.S.--making dire predictions of damage to the national economy, threats to security and loss of status in the world. There also seemed to be an attractive solution: coax more women to these traditionally male fields. But there was not much public discussion about the reasons more women are not pursuing careers in these fields until 2005, when then Harvard University president Lawrence Summers offered his personal observations.