The central finding may be summarized in a sentence. We found evidence of four price-revolutions since the twelfth century: four very long waves of rising prices, punctuated by long periods of comparative price-equilibrium. This is not a cyclical pattern. Price revolutions have no fixed and regular periodicity. Some were as short as eighty years; others as long as 180 years. They differed in duration, velocity, magnitude, and momentum.
