This study estimates and tests the endogeneity of the natural rate of growth using the balance-of-payments consistent rate of growth (BPCRG) instead of the actual rate of growth. Our approach is also theoretically compatible with the one proposed by Thirlwall (2001). Following this idea, we first calculated the BPCRG and then tested the Thirlwall’s Law for the U.S. economy. We then proceeded to test the endogeneity using the BPCRG. Empirical results we obtained support Thirlwall’s Law and endogeneity.