If the thesis of Progress & Poverty is correct, then the cyclic nature of civilization is due primarily to the tendency of the labor cost of acquiring unimproved land for productive workers to increase faster than the rate at which wages can be accumulated to acquire it. If this is the case, then the decline of our present phase of civilization may have begun in the 1930s, when state governments in the United States begun replacing property taxes with sales taxes, as the share of total government revenues raised from property taxes has now fallen from 40-50% to less than 10%, and the share is even lower in other countries.

However while the Roman Republic relied primarily a 1-3% annual property tax on wealth to fund its early expansion from 509BC, it had abandoned public assessed domestic property taxes by 167BC at the latest, yet the the Roman Empire reached its height in 117AD. So the point in time at which a country eliminates domestic property taxes on landed wealth in order to maximize the private capture of rent for its political class is unlikely to represent the peak or maximum of the civilization, but rather an initial inflection point, in which case a peak of our current phase of civilization during the 1960s may have been possible, with the inflection point occurring earlier.