4 AGEICULTUBAL PRICES 



ucts f rorn day to day and month to month, and noting when the re- 

 lationship is normal and when abnormal. In this way they will 

 acquire habits of intelligent observation of price trends that should 

 prove of very great value to them when they get into business for 

 themselves. 



If this book is used as a college text, it is hoped that it will be 

 by classes which are especially concerned in applying statistical 

 laws to agricultural prices. Such classes should have free access 

 to calculating machines, multiplying tables, etc., and should make 

 a serious effort to work out various ratios and also to work out 

 supply and demand laws for various farm products by means of 

 correlation coefficients, lines of regression, etc. The tables given 

 in the appendix should be of some value as a source of raw material. 

 For further material, it is suggested that the Year Books of the 

 United States Department of Agriculture, the Monthly Crop Re- 

 porters of the Bureau of Crop Estimates, and the Reports of the 

 Chicago Board of Trade be consulted. A good book on correla- 

 tion coefficients, etc., is Yule's Theory of Statistics. The teacher 

 of the suggested class in agricultural price statistics should sim- 

 plify the mathematics to mere method, not concerning himself or 

 his pupils with the theory back of it all. Wherever possible, the 

 teacher should study very carefully the January and April, 1919, 

 volumes of The Review of Economic Statistics, published by the 

 Harvard University Press. The methods as exemplified in these 

 volumes can very profitably be applied to the field of agricultural 

 prices. 



Acknowledgement is made to Professors J. M. Eward and E. 

 G. Nourse, of the Iowa State College, and to Professor F. A. Pear- 

 son, of the University of Illinois, for criticisms and helpful sug- 

 gestions. 



HENRY A. WALLACE. 



