The Natural

The real theory and the monetary theory seem to give the rate two masters. One locates it in the willingness to save and the opportunities to invest; the other follows the money market, the banks, and the terms on which liquidity can be obtained. A borrower, meanwhile, receives a single quotation. If the banks can alter that quotation, what has become of the real forces that were supposed to determine it? Knut Wicksell's answer, developed in 1898, was to distinguish the rate actually charged from the rate at which the economy's prices could remain at rest. The two could diverge, and their divergence would have consequences. Credit could be made available at a money price that encouraged more expenditure than the existing terms of production could sustain without a change in prices. The power to name the price of a loan was therefore real, but its exercise was not free of constraint. The natural rate gave the constraint a name.

Wicksell introduced the natural rate as the rate on loans neutral with respect to commodity prices, and related it to the return that would emerge if capital were lent in goods without the intermediation of money. In his simplified account, entrepreneurs bid for the use of resources and compare the expected proceeds with the cost of obtaining them. A loan rate held below the relevant normal level leaves an inducement to expand. More entrepreneurs try to command labor, materials, and goods; with the banking system accommodating their demands, prices are pressed upward. A rate held too high works in the opposite direction. The disturbance continues while the discrepancy is maintained: the famous cumulative process.¹ The adjective matters. This is more than a change in the price of one asset, or a single adjustment in the price level. It is a continuing pressure arising from terms of credit that keep expenditure out of line with the conditions under which resources are available. The normal rate is the point at which that particular pressure ceases.

The comparison is relative, and its benchmark moves. A money rate of four per cent might restrain one economy and encourage expenditure in another; a rise from three to four could even leave credit further below its normal level if productive opportunities had improved faster. Wicksell expressly warned against reading the stance of credit from the absolute number. He also refused to insist on an unqualified equality between two vaguely defined averages: according to the definition adopted, the risks of enterprise could require a wedge between the capital return and the loan rate.² These qualifications give the argument its practical force. The relevant question is what the rate does in the economy in which it operates. A banker cannot answer it simply by recalling that the same quotation once accompanied stable prices. Nor does a high rate prove that credit is scarce in the consequential sense. If the gains expected from putting resources to work have risen still more, the supposedly severe terms may continue to invite expansion.

The historical mechanism also contains limits that the image of an invisible anchor can obscure. Wicksell examines banks tied to one another, to reserves, to currency in circulation, and to an international gold standard. An individual bank cannot indefinitely offer terms different from every competitor without consequences for its business and position. A whole credit system faces a different question, and the ideal case of payments made entirely through bank credit gives the cumulative process greater freedom than a system constrained by circulating gold. The argument follows these differences rather than treating money creation as an unlimited command over real wealth.³ A loan can finance a claim on a resource; it cannot, by that act alone, create every resource the borrower seeks. That is why the distinction between the two rates is productive. It connects a monetary arrangement to the bids that arrangement makes possible. It does not turn every rise in prices, whatever its cause, into a complete diagnosis of the rate that banks ought to have charged.

A related benchmark survives as r-star, a neutral real rate. Holston, Laubach, and Williams define it as the real short-term rate consistent with output at its natural level and constant inflation. Their estimate is a slow-moving component inferred jointly with potential output and trend growth from output, inflation, and interest-rate data. It deliberately excludes some transitory disturbances; it is not a rate observed in a contract, or a sufficient prescription for every quarter. The estimates remain imprecise even with hindsight.⁴ The distinction between real and nominal is essential here. To compare a quoted policy rate with a real benchmark, one must account for expected inflation over the relevant interval. A four per cent quotation with three per cent inflation expected carries a different prospective cost in goods from the same quotation with one per cent expected. Merely placing the nominal number beside r-star would compare different measures of the price of time.

An unobserved benchmark need not be a useless one. It can organize an explanation that is tested against the behavior of several observed quantities. But a name does not remove the work of inference. The policy-maker has to distinguish a change in productive capacity from a change in demand, and a persistent alteration in the conditions of saving and investment from a passing disturbance. Different accounts can make the same movement of prices mean different things. The natural rate therefore disciplines a question more securely than it supplies a number: relative to what counterfactual would these financial conditions count as easy or tight? It supplies no independent moral warrant. A rate consistent with a model's stability conditions is not, for that reason, a fair return to every creditor, an affordable charge to every borrower, or the rate that best serves every public purpose. The word natural identifies a relation within an account of the economy. It cannot convert that account's assumptions into a judgment about what anyone deserves.

Wicksell's enduring move was to make the monetary quotation answerable to something beyond itself. The rate charged by banks could differ from the rate consistent with price stability, and that difference could help explain why expenditure and prices kept moving. Modern estimates give the old question a statistical form without making its object directly visible. The central bank can announce its own instrument; it has to infer the conditions against which the instrument operates. And the comparison is incomplete until the unit of account is made explicit. The borrower signs for money, while production, consumption, and repayment take place in a world whose prices change. The next plate separates the additional money promised by a loan from the additional purchasing power it delivers.⁵ The natural rate points toward a price of time measured in goods. To find that price inside a monetary contract, we must first determine how much of the quoted rate merely accompanies the changing worth of the money in which it is paid.