In order to uniquely determine the elastic thickness of the lithosphere, Te, from gravity and topography data, the coherence method explicitly assumes that surface and subsurface loads are statistically uncorrelated. In many realistic cases (e.g., mountain building) this assumption is likely to be violated. The results of Monte Carlo simulations designed to measure the bias and variance of Te estimates when the degree of correlation, R, between fractal surface and subsurface loads is not null are presented. According to the results, when there is no correlation between the loads, the estimated Te is in excellent agreement with the simulated Te. There is a strong likelihood of an upward bias in Te estimates if the dimensions of the study area are not adequate to fully resolve the longest wavelengths. The results indicate that the flexural behavior of the lithosphere to loading does not change significantly along the fold/thrust belt. -from Authors