The maintenance of the fertility of our soil is a matter of national concern. In the long run, it is of more vital interest to the people of the cities than to the farmer. Men engaged in industrial enterprises should do what they can to favor such adjustment of prices as will make it to the advantage of the farmer to keep his land in good heart, because that will make for larger production and more economical production. MEASURING TOTAL CROP PRODUCTION This chapter does not follow the same line of thought as the other chapters. It has an indirect bearing, however, and we believe the suggested method of measuring total crop production to be of some value. Small crops ordinarily bring the farming class more money than large crops. Nevertheless, in the long run big crops mean prosperity to the country as a whole. To judge just when crops as a whole are large and when they are small, a method has been devised, which may be illustrated as follows: In 1918, the United States produced 2,582,814,000 bushels of corn, 917,100,000 bushels of wheat, 89,833,000 tons of hay, 11,700,000 bales of cotton, etc. Now, to ascertain total crop production, it is obviously impossible to add together bushels, tons, bales, etc. We can add together the value of the crops, but the price level shifts from year to year, and this method is not satisfactory. Now, the 1907–1916 ten-year average price of corn was 61 cents, of wheat 96.2 cents, of hay $11.49 a ton, of cotton $59 a bale, etc. A ten-year average illustrates the relative economic emphasis. These prices are therefore used as constant factors, applicable to any crop year. The 1918 corn crop of 2,582,814,000 bushels, converted into economic crop units by multiplying by 61, equals 157,500,000,000. The 1918 wheat crop of 917,100,000 bushels, multiplied by 96.2, equals 63,600,000,000. The same thing done with the thirteen leading crops gives 559,900,000,000 crop units produced by the United States in 1918, or 5,270 crop units per capita. The per capita production of crop units since 1880 has been as follows: