Gradually typed programming languages aim to improve software maintenance by allowing programmers to selectively add type annotations to untyped programs. Run-time checks ensure that these typed portions interact soundly with unannotated parts of the program. These checks, however, may introduce unacceptable performance overhead. The extent of the overhead has not been systematically studied and no common methodology exists to diagnose such problems. In this position paper, we propose an idea for a framework for evaluating the performance of a gradual type system.