This paper examines evidence on the "systemic effects" of expanding school choice in Milwaukee, Wisconsin. Milwaukee is home to one of the nation's largest and longest-running school choice programs. If there are systemic effects from expanding school choice we should be able to see them in Milwaukee. This paper also introduces a novel method for analyzing systemic effects. Taking full advantage of student-level data, we develop a new measure of those effects based on the extent of voucher options that each student has each year. The idea behind this measure is that school systems face greater competitive pressure to serve students well when students have more options to leave. This type of measure might be useful for future analyses of systemic effects. Using this new approach, we find that students fare better academically when they have more options from Milwaukee's voucher program. The effects are modest in magnitude, but they are robust to multiple specifications of the model. (Contains 8 tables and 6 footnotes.) [For the EPIC review of this report, "Review of "The Effect of Milwaukee's Parental Choice Program on Student Achievement in Milwaukee Public Schools"", see ED530090.]