How many times did Atlas Shrug ? And where in the novel did Atlas Shrug?

The people really responsible for "holding the world up" so to speak are disappearing.Worsening the economic depression in the U.S. is the unexplained phenomenon of talented men retiring and disappearing. Every time a scientist or artist questions this dystopian system, they put their lives in danger. For example, Owen Kellogg, a bright young Taggart employee for whom Dagny had great hopes, tells her that he is leaving the railroad. McNamara, a contractor who was supposed to rebuild the Rio Norte Line, retires unexpectedly. As more great men disappear, the American people become increasingly pessimistic. Dagny dislikes the new phrase that has crept into the language and signifies people's sense of futility and despair. Every time these things happen, I suppose you could say "Atlas shrugged". Counting them would be tedious indeed.