There is tremendous interest among policymakers and advocates in diversifying the teacher labor market. This interest is driven at least in part by a growing body of research that points to the benefits of diverse teachers, particularly for students of color. While the diversity of the teacher workforce in the United States has increased in recent decades, it is still lags far behind the diversity of the nation's students. To better understand the issue and what can be done about it, we simulate how varying levels of diversity at different points in the path to becoming a teacher affect the diversity of early-career teachers. Our simulations suggest that the lack of teacher diversity is due less to high school or college graduation disparities and more to the choices of college students about whether to pursue teacher preparation programs and become teachers. We also find that increases in the retention of teachers of color have relatively little impact on the diversity of the workforce: even if schools retained 100 percent of their early-career teachers of color, it would only increase workforce diversity by about 4 percentage points.