Compare the same country in different times, and the same relation is obvious. As the result of much investigation, Hallam says he is convinced that the wages of manual labor were greater in amount in England during the middle ages than they are now. Whether this is so or not, it is evident that they could not have been much, if any, less. The enormous increase in the efficiency of labor, which even in agriculture is estimated at seven or eight hundred per cent., and in many branches of industry is almost incalculable, has only added to rent. The rent of agricultural land in England is now, according to Professor Rogers, 120 times as great, measured in money, as it was 500 years ago, and 14 times as great, measured in wheat; while in the rent of building land, and mineral land, the advance has been enormously greater. According to the estimate of Professor Fawcett, the capitalized rental value of the land of England now amounts to £4,500,000,000, or $21,870,000,000—that is to say, a few thousand of the people of England hold a lien upon the labor of the rest, the capitalized value of which is more than twice as great as, at the average price of Southern negroes in 1860 would be the value of her whole population were they slaves. In Belgium and Flanders, in France and Germany, the rent and selling price of agricultural land have doubled within the last thirty years.[43] In short, increased power of production has everywhere added to the value of land; nowhere has it added to the value of labor; for though actual wages may in some places have somewhat risen, the rise is clearly attributable to other causes. In more places they have fallen—that is, where it has been possible for them to fall—for there is a minimum below which laborers cannot keep up their numbers. And, everywhere, wages, as a proportion of the produce, have decreased.