Women typically produce more dispersed vowels than men. This sex difference makes predictions about the role of each sex in vowel changes. Specifically, women lead changes that maintain the distance between vowels, such as chain shifts, while men lead changes that reduce the distance between vowels, such as vowel mergers. That women lead chain shifts is well-established. That men lead mergers has not been established. An investigation of vowel mergers among the Atlas of North American English speakers reveals that men do lead mergers, and that speakers with a less dispersed vowel system show more instances of mergers, regardless of sex. I conclude by positing vowel dispersion as an internal explanation of which sex leads a vowel change.