7.7.2 Elliptical Comparisons
The conjunction than often introduces an abridged expression (eg, “You are younger than I [am young]).” Correct placement of than is important to avoid ambiguity:
Women are more likely to take vitamins than men. [Are women more likely to consume vitamins than men are, or are women more likely to consume vitamins than they are to consume men?]
Women are more likely than men to take vitamins.