The Wealth of Nations by Part 1 Chapter 7 Page 22

together, and in whole classes of employments, keep up the market price of particular commodities above the natural price, and maintain both the wages of the labour and the profits of the stock employed about them somewhat above their natural rate.

Such enhancements of the market price may last as long as the regulations of police which give occasion to them.

The market price of any particular commodity, though it may continue long above, can seldom continue long below its natural price.

Whatever part of it was paid below the natural rate, the persons whose interest it affected would immediately feel the loss, and would immediately withdraw either so much land, or so much labour, or so much stock, from being employed about it, that the quantity brought