Many commentators purport to use the Kemp-Wan Theorem to discuss the e
ffects of regional integration schemes on non-member countries, and to
operationalize the theorem in terms of the share of member countries'
imports coming from non-members. I show that Kemp and Wan say nothing
about changes in non-member welfare and that the latter is more close
ly related to non-members' imports than to their shares of members' ma
rkets. I suggest that a new approach to this issue is required.