( 56 )
our experience, by the variable value of the commodities produced by a given quantity of labour, compared with the constant value of such labour; and that profits never, on any occasion, rise or fall, unless the value of the produce of a given quantity of labour rises or falls, either from the temporary or ordinary state of the demand and supply.
On the subject of the distinction between wealth and value, it would show, that though they are by no means the same, they are much more closely connected than they have of late been supposed to be; and that the best practical measure of the relative wealth of different countries would be the quantity of common labour which the value of the whole annual produce of each country would enable it to command at the actual price of the time, which in some rich countries might amount to above double the number of families actually employed, and in poor countries might not greatly exceed such number.
On the subject of foreign trade, it would show that its universally acknowledged effect in giving a stimulus to production, generally, is mainly owing to its increasing the value of the produce of a country's labour by the extension of demand, before the value of its labour
