July 24, 1914] 



SCIENCE 



123 



errors. It is unfortunate that the Bureau did 

 not adjust its figures to the census basis in 

 1899. This has been done since 1909 so that 

 we may expect a much smaller error in the 

 future as the error will be corrected at each 

 census year. 



each year to be corrected so that the error 

 from year to year would not be cumulative. 



ARE OUR CROP YIELDS DECREASING? 



In the same issue Dr. Hopkins discusses 

 the question of crop yields. The conclusion 



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110 

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riG. 1. 



ComparatiTe crop yields for the United States eajst of the Mississippi Eiver. Yield of 1866 con- 

 sidered as 100 per cent. 



The writer believes that the accuracy of the 

 reports could be greatly increased if there 

 were added to the present method of reporting 

 a system of reports by farmers on actual areas 

 grown and yields received. If the Bureau of 

 the Census could send a large number of 

 letters to farmers each winter asking for the 

 area of the farms, area of each crop grown and 

 total yield, these reports could be compared 

 with reports from the same farms for previ- 

 ous years. The changes in areas of farms, 

 failures of some men to report and other 

 problems involved, would not, in the writer's 

 opinion, be at all insurmountable. This in- 

 formation would allow the final report for 



is reached that for the ten years 1899 to 1909, 

 " An increase of 15.^^ per cent, in farmed land 

 with an increase of only 1.7 per cent, in pro- 

 duction reveals the truth of reduced yield per 

 acre." 



This conclusion is based on serious errors 

 in the use of statistics. The production used 

 is the total bushels of cereals. The acreage 

 used is the area of improved land in farms. 

 This land is not aU farmed, much less is it all 

 planted' to cereals. 



The census report states that 



Improved land includes all land regularly tUled 

 or mowed, land pastured and cropped in rotation, 

 land lying fallow, land in gardens, orchards, vine- 



