1. INTRODUCTION  
2. WFIRST  
2.1. Goals of the WFIRST Microlensing Survey  
2.2. Evolution of the WFIRST Mission: Design Reference Missions, AFTA, and Cycle 7  
2.3. The WFIRST Microlensing Survey  
3. SIMULATING THE WFIRST MICROLENSING SURVEY  
3.1. Galactic Model  
3.2. Normalizing the event rate  
3.3. The WFIRST fields  
4. EVALUATING THE EFFECT OF CHANGES TO MISSION DESIGN ON PLANET YIELDS  
4.1. Analytic estimates of the change in yield  
4.2. Testing Analytic Estimates: Bandpass  
4.3. Testing Analytic Estimates: Background light  
4.4. Applying analytic estimates: Optimizing Field Selection for Cycle 7  
5. DISCUSSION  
5.1. Simulation Uncertainties  
5.2. Galactic model uncertainties  
5.3. Planet Population Uncertainties  
5.4. Future Improvements  
6. CONCLUSION