Originally Posted by RChung

Close. Ordered rank to occurrence (in this case, to death). Proportional hazards is, um, proportional, and Cox realized that proportionality is a strong enough restriction that you can get the risk ratios even without needing the underlying absolute risk. I *think* I might be one of the few professors who forces students to sit through a lecture where I do a proportional hazards estimation with two covariates on the blackboard by hand. Like most survival analysis techniques, it handles censored observations pretty well.