An article of faith among central bankers is that negative interest rates will stimulate spending by consumers and businesses, ending the stagnant growth that has plagued many of the world’s biggest economies. Short-term rates are zero or negative in much of Europe and Japan, and even the Federal Reserve holds out the possibility of bringing rates below zero in the event of a downturn. This policy is almost assuredly counter-productive. It very likely stimulates saving, especially in the context of an aging population, and it distorts the allocation of resources over time and across the risk classes to which saving is applied.

Real vs. Nominal Rates

A preliminary consideration is the distinction between the so-called nominal or stated interest rates, those quoted by banks and bond sellers, and real interest rates, which are net of expected inflation. If the short-term nominal interest rate is zero, but expected inflation is -2%, then the real interest rate is +2%. If expected inflation is +2%, then the real interest rate is -2%. When negative rates are discussed in the media, they generally refer to nominal rates, and central bank interest rate targets are discussed in nominal terms. Again, some central banks are targeting very low or slightly negative nominal rates today. In most of these cases, inflation is low but positive, indicating that real interest rates are negative. With that said, it’s important to note that the discussion below relates to real interest rates, not nominal rates, despite the fact that central banks explicitly target the latter.

Saving Behavior

Most macroeconomists casually assume that lower interest rates discourage saving and thus stimulate spending. However, this is being called into question by observers of recent central bank actions around the world. Those actions have been relatively futile in stimulating spending thus far. In fact, data suggest that the negative-rate policies might be increasing saving rates. These points are discussed in “Are Negative Rates Backfiring? Here’s Some Early Evidence” in the Wall Street Journal (or this Google search if the first link fails).

An examination of the microeconomic foundations of the standard treatment of saving behavior shows that it requires some limiting assumptions. We all face constraints in meeting our future income goals: our current income imposes a limit on what we can save, and the rate of return we can earn on our funds limits what we can accumulate over time from a given level of saving. Those constraints must be balanced against an individual’s preferences for present pleasure relative to future gain.

Time Preference

The rate at which agents are willing to sacrifice future for present consumption is often called the rate of time preference. This differs from one individual to another. A high rate of time preference means that the individual requires a large future reward to induce them to set aside resources today, foregoing present consumption. A low rate of time preference means that little inducement is necessary for saving, so the individual is “thrifty”. It’s generally impossible to directly observe differing rates of time preference across individuals, but they reveal their preferences for present and future consumption via their saving (or borrowing) behavior. If an individual saves more than another with an equal income, it implies that the first has a lower rate of time preference at a given level of present consumption.

Substitution and Income Effects

A lower interest rate always creates a tendency to substitute present for future consumption. That’s because the change is akin to an increase in the price of future consumption. However, that substitution might be offset, or more than offset, by the fact that total achievable lifetime income is diminished: the lower rate at which the individual’s use of resources can be transferred from the present to the future means that some sacrifice is necessary. In other words, the negative “income effect” might cause consumers to reduce consumption in the future and in the present! Thus, saving may increase in response to a lower interest rate. Perhaps that tendency will be exaggerated if rates turn negative, but it all depends on the shape of preferences for present versus future consumption.

Which of these two effects will dominate? The substitution effect, which increases present consumption and reduces saving? Or the income effect, which does the opposite? Again, consumers are diverse in their rates of time preference. There are borrowers who prefer to have more now and less later, and savers who might wish to equalize consumption over time or accumulate assets in pursuit of other goals, such as bequests. A shift from a positive to a negative interest rate would reward borrowers who wish to consume more now and less later. Both their substitution and income effects on present consumption would be positive! In fact, spending by that segment might be the only unambiguously stimulative effect from negative rates. But individuals with low rates of time preference are more likely to spend less in the present, and save more, after the change. Two individuals with identical substitution effects in response to the shift to negative rates may well differ in their income effects: the largest saver of the two will suffer the largest negative income effect.

Ugly Intervention

These uneven impacts on saving are a testament to the pernicious effects of central bank intervention leading to negative rates. Savers are punished, while those who care little about self-reliance and planning for the future are rewarded. Of course, at an aggregate level, saving out of income is positive, so on balance, agents demonstrate  that they have sufficiently low rates of time preference to qualify for some degree of punishment via negative rates. After all, savers will unambiguously suffer a decline in lifetime income given the shift to negative rates.

The Necessity of Thrift

The fact that a standard macroeconomic treatment of saving ignores negative income effects at very low rates of interest is surprising given the very nature of thrift. Savers obviously view future consumption as something of a necessity, especially as they approach retirement. Present and future consumption are locally substitutable, but large substitutions come only with great pain, either now or later. Another way of saying this is that present and future consumption behave more like complements than substitutes. (A more technical treatment of this distinction is given in “Complementarity, Necessity and Preferences“, by Steven R. Beckman and W. James Smith.) This provides a basic rationale for a conflicting assumption often made in macroeconomic literature: that economic agents attempt to “smooth” their consumption over time. If present and future consumption are treated as strict complements, there is no question that the income effect of a shift to negative  rates will increase saving by those who already save.

This is not to imply that savers always respond to lower rates by saving more. In “Choice between Present Consumption and Future Consumption“, Supriya Guru asserts that empirical evidence for the U.S. suggests that the substitution effect dominates. However, extremely low or negative interest rates are a recent phenomenon, and empirical evidence is predominantly from periods of history with much higher rates. Moreover, the advent of very low rates is coincident with demographic shifts favoring more intense efforts to save. The aging populations in the U.S., Europe and Japan might reinforce the tendency to respond to negative rates by saving more out of current income.

Risk As a Relief Valve

Another complexity regarding the shape of preferences is that consumers might never be willing to substitute present consumption for less in the future. That is, their rate of time preference may be bounded at zero, even if the interest rate imposed by the central bank is negative. An earlier post on Sacred Cow Chips dealt with this issue. In that case, saving will increase with a shift to negative rates under two conditions: 1) there is a minimal level of future consumption deemed a necessity by consumers; and 2) that level exceeds the consumption that is possible without saving (endowed or received via transfers). That outcome represents a “corner solution”, however. Chances are that consumers, having been forced to accept an unacceptable tradeoff at negative “risk-free” rates, will lean more heavily on other margins along which they can optimize, such as risk and return.

That eventuality suggests another reason to suspect that very low or negative rates are not stimulative: savers face a range of vehicles in which to place their funds, not simply deposits and short-term money market funds earning low or negative yields. Some of these alternatives earn much higher returns, but only at significant risk. Nevertheless, the poor returns on safe alternatives will lead some savers to “reach for yield” by accepting high risks. That is a rational response to the conditions imposed by central banks, but it leads consumers to accept risk that is otherwise not desired, with a certain number of consumers suffering dire ex post outcomes. It also leads to an allocation of the economy’s capital that is riskier than would otherwise occur.

Furthermore, as mentioned in the WSJ article linked above, consumers might regard negative rates as a foreboding signal about the economic future. The negative rates are bad enough, but even reduced levels of future consumption might be under threat. Thus, risk aversion might lead to greater saving in the context of a shift to negative rates.

Corporate Saving and Capital Investment

A great deal of saving in the economy is done by corporate entities in the form of “undistributed corporate profits”, or retained earnings. It must be said that these flows are not especially dependent on short-term yields, even if those yields have a slight influence on corporate management’s view of the opportunity cost of equity capital. Rather, those flows are more dependent on the firm’s current profitability. To the extent that very low or negative interest rates discourage consumption, their effect on current profitability and the perceived profitability of new business capital projects cannot be positive. To the extent that very low or negative rates portend risk, their effect on capital investment decisions will be negative. Savings out of personal income and from retained earnings is likely to exceed the amount required to fund desired capital investment. The funds accumulated in this way will remain idle (excess working capital) or be put toward unproductive uses, as befits an environment in which real returns are negative.

We Gotta Get Out of This Place

Central banks will be disappointed that the primary rationale for their reliance on negative interest rates lacks validity, and that the policy is counterproductive. Statements from Federal Reserve officials indicate that the next expected move in their interest rate target will be upward. However, they have not ruled out negative rates in the event that economic growth turns down. Perhaps the debate over negative rates is still raging inside the Fed. With any luck, and as evidence piles up from overseas on the futility of negative rates, those arguing for a “normalization” of rates at higher levels will carry the day.