Equal quantities of labour will at distant times be purchased more nearly with equal quantities of corn, the subsistence of the labourer, than with equal quantities of gold and silver, or perhaps of any other commodity. Equal quantities of corn, therefore, will, at distant times, be more nearly of the same real value, or enable the possessor to purchase or command more nearly the same quantity of the labour of other people. They will do this, I say, more nearly than equal quantities of almost any other commodity; for even equal quantities of corn will not do it exactly. The subsistence of the labourer, or the real price of labour, as I shall endeavour to show hereafter, is very different upon different occasions; more liberal in a society advancing to opulence, than in one that is standing still; and in one that is standing still, than in one that is going backwards. Every other commodity, however, will at any particular time purchase a greater or smaller quantity of labour in proportion to the quantity of subsistence which it can purchase at that time. A rent therefore reserved in corn is liable only to the variations in the quantity of labour which a certain quantity of corn can purchase. But a rent reserved in any other commodity is liable, not only to the variations in the quantity of labour which any particular quantity of corn can purchase, but to the variations in the quantity of corn which can be purchased by any particular quantity of that commodity.
Though the real value of a corn rent, it is to be observed however, varies much less from century to century than that of a money rent, it varies much more from year to year. The money price of labour, as I shall endeavour to show hereafter, does not fluctuate from year to year with the money price of corn, but seems to be everywhere accommodated, not to the temporary or occasional, but to the average or ordinary price of that necessary of life. The average or ordinary price of corn again is regulated, as I shall likewise endeavour to show hereafter, by the value of