Simple Function Point is a functional size measurement method that can be used in place of IFPUG Function Point, but requires a much simpler - hence less time and effort consuming - measurement process. Simple Function Point was designed to be equivalent to IFPUG Function Point in terms of numerical results. This paper reports an empirical study aiming at verifying the effectiveness of Simple Function Point as a functional size measurement method, especially suitable to support estimation of software development effort. The data from a large popular public dataset were analyzed to verify the correlation of Simple Function Point with IFPUG Function Point, and the correlation of both size measures to development effort. The results obtained confirm, at a reasonable level of confidence, the hypothesis that Simple Function Point can be effectively used in place of IFPUG Function Point.