My uneducated guess on this is that the early 1980s is when computing went from an academic and intellectual pursuit to something where you could make giant pil

My uneducated guess on this is that the early 1980s is when computing went from an academic and intellectual pursuit to something where you could make giant piles of money. If (for various social and possibly psychological/biological reasons) men have a higher tendency to flood into highly-remunerated fields regardless of underlying interest/capability, you might see participation looking something like: 1970s: 20,000 "nerds" with equal gender distribution M: 10,000 (50%) W: 10,000 (50%) 1990s: 200,000 "nerds" with equal gender distribution + 800,000 men primarily focused on money M: 900,000 (90%) W: 100,000 (10%) Edit: this theory doesn't deny the argument that CS as a field became particularly uninviting to women over this time period as well, but the causality goes: men enter field for the $ => increasingly skewed gender ratio => male-centric culture develops => even women "nerds" stop joining because environment has become unfamiliar at best and hostile at worst