The Wealth of Nations by Part 5 Chapter 2 Page 36

The advantage, however, which the landlord has derived from the invariable constancy of the valuation by which all the lands of Great Britain are rated to the land-tax, has been principally owing to some circumstances altogether extraneous to the nature of the tax.

It has been owing in part to the great prosperity of almost every part of the country, the rents of almost all the estates of Great Britain having, since the time when this valuation was first established, been continually rising, and scarce any of them having fallen. The landlords, therefore, have almost all gained the difference between the tax which they would have paid according to the present rent of their estates, and that which they actually pay according to the ancient valuation. Had the state of the country been different, had rents been gradually