Recent Pulsar Timing Array (PTA) upper limits on the gravitational wave strain in the nanohertz frequency band are impacting our understanding of the binary supermassive black hole population. But as upper limits grow more constraining, what can be implied about galaxy evolution? In this talk, I will present simulations which answer this question. Specifically, these simulations are used to investigate which astrophysical parameters have the largest impact on gravitational strain predictions and provide a simple framework to directly translate between measured values for the parameters of galaxy evolution and PTA limits, including the M-M_bulge relation and binary stalling. Additionally, these simulations can be used to investigate the potential of using electromagnetic (EM) observations of binary supermassive black holes to characterize the statistics of the binary population.