Explain in words what is meant by the \"single wage property\". How does it arise from our simple model of labor market equilibrium? Do you think this is a realistic prediction of our model, given our class discussion on (1) the evidence on wage convergence within the U.S. and (2) the persistent wage gaps between different countries? What could be the cause of these persistent gaps, i.e. which fundamental assumptions underlying our model may be unrealistic in the real world