Measurements of the demographics of exoplanets over a range of planet and host star properties provide fundamental empirical constraints on theories of planet formation and evolution. Because of its unique sensitivity to low-mass, long-period, and free-floating planets, microlensing is an essential complement to our arsenal of planet detection methods. I summarize the results to date from microlensing surveys, and discuss the expectations from near-future ground-based surveys. I then discuss efforts to combine results from microlensing, radial velocity, and direct imaging surveys to constrain the distribution of planets over roughly four orders of magnitude in planet mass and nearly five orders magnitude in period. Finally, I motivate a microlensing survey with WFIRST, which when combined with the results from Kepler, will yield a nearly complete picture of the demographics of planetary systems throughout the Galaxy.
Host: Sara Seager