One indication that our methodology does a good job adjusting for societal change is that the resulting time series matches up with the time series in landfall frequencies and intensities. If there were a significant bias in our methods (for whatever reason) it would show up as a deviation between the normalized trends and the geophysical trends. We see no such deviation. Other reasons for confidence in our analysis is that it has been independently replicated on several occasions and that we (and others) can also recover an ENSO signal in the data (e.g., PDF).
You can play around with the data from the ICAT Damage Estimator. Details on the analysis can be found in the following paper:
Pielke, Jr., R. A., Gratz, J., Landsea, C. W., Collins, D., Saunders, M., and Musulin, R., 2008. Normalized Hurricane Damages in the United States: 1900-2005. Natural Hazards Review, Volume 9, Issue 1, pp. 29-42.