In this volume Professor Moore again makes use of his characteristic method, developed in his earlier volume on Laws of Wages. The method, in brief, is to derive economic laws inductively from statistics by means of the modern refined methods of the calculus of probabilities. The specific problem in the present instance is to derive the law of business cycles of expansion and depression from data as to rainfall, crops, and prices.

First, by an application of Fourier's formula to data as to rainfall in the Ohio valley and in Illinois, he finds that the annual rainfall obeys a compound cyclical law based on cycles of eight and thirty-three years. He then correlates the rainfall at the critical period of growth for each crop with the total yield and with the yield per acre of the principal staple crops. These in turn are correlated with prices of pig iron and with general prices. The laws which he derives from this analysis may be briefly stated as follows. The annual rainfall, as just stated, obeys a law of compound cycles of eight and thirty-three years’ duration. The yield of the great staple crops, both the gross yield and the yield per acre, obeys a similar law, presumably in the relation of cause and effect.