  Gender bias in computing is a hard problem that has resisted decades of
research. One obstacle has been the absence of systematic data that might
indicate when gender bias emerged in computing and how it has changed. This
article presents a new dataset (N=50,000) focusing on formative years of
computing as a profession (1950-1980) when U.S. government workforce statistics
are thin or non-existent. This longitudinal dataset, based on archival records
from six computer user groups (SHARE, USE, and others) and ACM conference
attendees and membership rosters, revises commonly held conjectures that gender
bias in computing emerged during professionalization of computer science in the
1960s or 1970s and that there was a 'linear' one-time onset of gender bias to
the present. Such a linear view also lent support to the "pipeline" model of
computing's "losing" women at successive career stages. Instead, this dataset
reveals three distinct periods of gender bias in computing and so invites
temporally distinct explanations for these changing dynamics. It significantly
revises both scholarly assessment and popular understanding about gender bias
in computing. It also draws attention to diversity within computing. One
consequence of this research for CS reform efforts today is data-driven
recognition that legacies of gender bias beginning in the mid-1980s (not in
earlier decades) is the problem. A second consequence is correcting the public
image of computer science: this research shows that gender bias is a contingent
aspect of professional computing, not an intrinsic or permanent one.
