Near the beginning of the minutes of the January meeting of the Federal Open Market Committee (FOMC), released yesterday, you'll find a reiteration of the FOMC's historic decision explicitly endorsing a numerical definition of long-run price stability:

"The inflation rate over the longer run is primarily determined by monetary policy, and hence the Committee has the ability to specify a longer-run goal for inflation. The Committee judges that inflation at the rate of 2 percent, as measured by the annual change in the price index for personal consumption expenditures, is most consistent over the longer run with the Federal Reserve's statutory mandate."

The minutes include the motivating force behind this decision:

"The Chairman noted that the proposed statement did not represent a change in the Committee's policy approach. Instead, the statement was intended to help enhance the transparency, accountability, and effectiveness of monetary policy."

In a speech given Tuesday at New College in Sarasota, Fla., our local participant in this decision—Atlanta Fed President Dennis Lockhart—provided his interpretation of this numerical inflation objective:

"The 2 percent inflation target is an aid to understanding how the FOMC will react to developments in the economy within an overarching approach that can be called 'flexible inflation targeting.'

"The word 'flexible' describes and qualifies the committee's exercise of judgment in reaction to adverse developments. The word 'flexible' also reflects the principle that it is not always feasible or desirable to hit the target in the short run. Short-lived shocks to the economy can temporarily move measured inflation well away from the 2 percent target."

The thinking behind that statement can be clearly seen in the following chart, which illustrates the volatility of annualized inflation rates as the horizon extends from one to five years:


As the chart shows, volatility noticeably declines as the horizon extends beyond one year to two years, and a similar decline occurs as we move from a two- to five-year horizon. This picture is exactly the type you would expect if inflation were subject to temporary ups and downs that dissipate over time. In his speech, President Lockhart offered his thoughts on the policy meaning of an inflation process that has this characteristic:

"Consider last year's energy and commodity price increases. Those cost pressures pushed up inflation in the early part of the year. Then, as expected, their influence dissipated as the year progressed.

"Had the FOMC tightened monetary policy early last year in response to the inflation threat, we might have compromised progress on growth and employment to no particular benefit with respect to our inflation mandate…

"As I see it, this is a recent, real-world example of a balanced approach in action. It illustrates the idea of flexible inflation targeting."

Of course, that particular example might ring somewhat hollow if the record suggested that the FOMC just got lucky this time around. A criticism that emerged in the aftermath of the inflation target announcement was not so much that it was flexible per se, but that in its focus on an undefined long-run, it is essentially an empty commitment. That opinion was offered in a Financial Times article penned by Lorenzo Bini Smaghi:

"The first [question about the FOMC's definition of price stability] relates to the time horizon over which the Fed is supposed to achieve price stability, namely the long-run. This differs from most other central banks in advanced economies, where price stability is targeted over a horizon of two to three years…

"Monetary policy produces its effects with lags of one to three years. This is the period over which the central bank should be held accountable."

That thought was echoed on The Economist's Free Exchange blog:

"According to the Fed's projections, it hits its target—2% inflation—over the long term. Mr Bini Smaghi's point is that it doesn't make much sense to judge current Fed actions against a long-run inflation projection.

"…the Fed doesn't necessarily run into problems of inconsistency if it projects inflation above 2% 1 or 2 years from now—a timeframe over which markets readily understand this group of policymakers to have control—while maintaining the long-run 2% goal."

The second part of The Economist comments move the conversation to an operational middle ground between an inflexible commitment to a target in the very short run and a promise that provides little discipline because its attainment remains out in a perpetually undefined future.

In particular, think about monitoring policy performance against a stated inflation objective over some "medium-term" horizon. "Medium-term" is itself a term of art, but I find it attractive to think about a three- to five-year horizon. Given the continuous arrival of shocks to the economy, uncertainties about the timing of policy effects, and the desirability of trading off precise control over inflation against the risks of destabilizing influences on real economic growth, I think it is still unrealistic and unwise to expect that an inflation target will be hit precisely even over a medium-run horizon. This is the reason, I believe, that an exact point target for inflation is relegated to the long run. But I think it is realistic, and wise, to expect realized average inflation to fall within a reasonable tolerance range about a long-run target over something like a three-to-five-year medium-term horizon.

People can disagree about what constitutes a reasonable tolerance range, but one option that I find sensible would be along the lines of the average volatility of medium-term inflation (calculated over a period in which inflation outcomes were deemed to be acceptable, which I've chosen to be the period since the mid-1990s). With this in mind, the following chart plots realized inflation over three-, four-, and five-year horizons. (For reference, the chart highlights the 2 percent target with upper and lower limits that are plus and minus 1 percentage point.)


The plus or minus 1 percentage point threshold in the above graph is somewhat above the standard deviation of medium-term outcomes shown in my earlier chart, so one might want to tighten up the bounds. But if you are willing to accept that it's close to your definition of tolerable deviation, the record does support the position that, over the past two decades or so, the Fed has delivered on the its now-explicit long-term objective, or taken sufficient to steps to correct matters when it wasn't.

Looking forward, if the midpoint of FOMC participants' most recent inflation projections comes to pass, the four- to five-year averages would remain near the long-run objective, with the three-year average moving away from its recent flirtation with the lower end of my hypothetical tolerance range.

I'm not saying that the above chart alone defines "appropriate policy"; performance against the other half of the dual mandate is obviously relevant. But I think it provides at least one way to think about what success looks like, and a sensible metric for whether the Fed is delivering on its long-run promise.

David AltigBy Dave Altig, senior vice president and research director at the Atlanta Fed