This monograph attempts two things: first, a detailed analysis of monthly data for a single cycle of prosperity and depression; second, a comparative analysis of monthly data in the three great industrial nations of the world, the United States, Great Britain and Germany. The secular and seasonal fluctuations are eliminated, for the work is concerned with cyclical fluctuations. The method used is to construct relative or index numbers from the actual data by using a new base for each of the twelve months of the year. The average of the actual figures for each January in the seven-year period is used as the base for January data, the average of the actual figures for the seven Februarys is used as the base for February data, and so on. The author selected twenty-three series of monthly data for the United States, fifteen for Great Britain, and fifteen for Germany. The Pearsonian coefficient was used to establish correlation, and to determine whether the series are synchronous or whether there is a lag, and if so how much of a lag. To test the relative position of each series in the cycle of prosperity and depression, a large number of correlations were worked out. Three main groups were finally selected, the Investment, Industrial, and Banking Groups.The author's groupings in the business cycle differ from those of Brookmire, Babson, and Professor Pearsons. This part of the study will interest students of business statistics and those who follow the reports of the above mentioned statistical services.In the fourth chapter the author reviews the various theories of prosperity cycles and then concludes with the statement: "The analysis of monthly data presented in the foregoing pages would indicate the following points: "1. That the first movement in the prosperity cycle begins with reserves, loans, deposits and money rates."2. That the movement of reserves, loans, deposits and money rates is the causal factor working out its influence on stock and bond prices, transactions on the stock exchange, bank clearings, business failures, building, employment, production, imports and exports, prices and profits."The monograph contains twelve charts and eleven tables and a bibliography. The work is a distinct contribution to economic statistics and will be useful to students of economics and business men who are interested in business forecasting.-"The South Atlantic Quarterly," Volume 21