Richard Cantillon's Analysis of the Price-Specie-Flow Mechanism Is Superior to David Hume's Analysis

Hume's most important contribution is his elucidation of monetary theory, in particular his clear exposition of the price-specie-flow mechanism that equilibrates national balances of payments and international price levels. In monetary theory proper, Hume vivifies the Lockean quantity theory of money with a marvellous illustration, highlighting the fact that it doesn't matter what the quantity of money may be in any given country: any quantity, smaller or larger, will suffice to do money's work of facilitating exchange. Hume pointed up this important truth by postulating what would happen if every individual, overnight, should find the stock of money in his possession to have doubled miraculously:

For suppose that, by miracle, every man in Great Britain should have five pounds slipped into his pocket in one night; this would much more than double the whole money that is at present in the kingdom; yet there would not next day, nor for some time, be any more lenders, nor any variation in the interest.

Prices then, following Locke's quantity theory of money, will increase proportionately.

The price-specie-flow mechanism is the quantity theory extrapolated into the case of many countries. The rise in the supply of money in country A will cause its prices to rise; but then the goods of country A are no longer as competitive compared to other countries. Exports will therefore decline, and imports from other countries with cheaper goods will rise. The balance of trade in country A will therefore become unfavourable, and specie will flow out of A in order to pay for the deficit. But this outflow of specie will eventually cause a sharp contraction of the supply of money in country A, a proportional fall in prices, and an end to, indeed a reversal of, the unfavourable balance. As prices in A fall back to previous levels, specie will flow back in until the balance of trade is in balance, and until the price levels in terms of specie are equal in each country. Thus, on the free market, there is a rapidly self-correcting force at work that equilibrates balances of payments and price levels, and prevents an inflation from going very far in any given country.

While Hume's discussion is lucid and engaging, it is a considerable deterioration from that of Richard Cantillon. First, Cantillon did not believe in aggregate proportionality of money and price level changes, instead engaging in a sophisticated micro-process analysis of money going from one person to the next. As a result, money and prices will not rise proportionately even in the eventual new equilibrium state. Second, Cantillon included the ‘income effect’ of more money in a country, whereas Hume confined himself to the aggregate price effect. In short, if the money supply in country A increases, it will equilibrate not only by prices rising in A, but also by the fact that monetary assets and incomes are higher in A, and therefore more money will be spent on imports. This income or more precisely, the cash balance, effect will generally work faster than the price effect.

—Murray N. Rothbard, An Austrian Perspective on the History of Economic Thought, vol. 1, Economic Thought Before Adam Smith (Auburn, AL: Ludwig von Mises Institute, 2006), 426-427.