Is the Phillips curve breaking down? Tight labor markets have historically tended to place upward pressure on wages and inflation. And the Phillips curve, a theory embodying the inverse relationship between inflation and unemployment, has been the cornerstone of modern monetary policy.

Yet U.S. CPI and wage inflation remain modest today, despite a nearly eight-year U.S. economic expansion and an unemployment rate that has already dropped below the Federal Reserve’s estimated “natural rate of unemployment” (the “equilibrium” long-run level of unemployment, often used interchangeably with the “non-accelerating inflation rate of unemployment,” or NAIRU). This casts doubt on the importance of labor market slack as a driver of inflation.

It’s important to note that future realized inflation depends on both historically realized inflation and inflation expectations. Phillips curve believers – unable to explain the low inflation rate in the current setting – might argue that this is because U.S. inflation expectations are very well anchored. Indeed, studies have documented that the weight of long-term expectations in the Phillips curve has risen steadily since the mid-1980s, while the slope of the Phillips curve has substantially declined, and the curve today could be flat.¹

Make no mistake, a flat Phillips curve would be a welcome development for the Fed, if inflation were on target. The reason is fairly straightforward: If people expect long-term inflation to be stable, wages won’t react as much to near-term changes in labor market slack. In this scenario, if a shock were to push inflation up, then anchored expectations would push it back down without the need for monetary tightening (and vice versa).²  

But here’s the hitch: Even though U.S. inflation expectations are supposed to be very well anchored, no one can tell where.

An elusive anchor

So what are some of the possibilities?

Looking at core personal consumption expenditure (PCE) inflation (see Figure 1), the Fed’s preferred benchmark, one could speculate that the U.S. is well anchored at 1.5% – not the 2% Fed target – just as Japan and the eurozone appear solidly anchored below target at 0% and 1%, respectively. Here the Fed usually points to professional surveys of inflation expectations, which tend to show somewhat higher values. Yet professional forecasters’ longer-term expectations have exceeded realized inflation almost 70% of the time since the early 1990s (when records began).³

Similarly, the Fed has been systematically discounting low market-based inflation expectations, attributing them to either reduced liquidity in the Treasury Inflation-Protected Securities (TIPS) market or to changes in the inflation risk premium. We disagree with the Fed here. As we’ve pointed out in the past, the distribution of potential inflation outcomes – and market perceptions of the likelihood of downside or upside misses – is at least as relevant as the mode, if not more. The latest research from the European Central Bank (ECB) suggests that a negative inflation risk premium is associated with strong deflation risk, rather than low inflation uncertainty.⁴ In essence, the market assigns a higher probability to the Fed’s missing to the downside.

To further complicate matters, prolonged deviations of inflation from the target may eventually de-anchor expectations, and it’s hard for anyone to know what margin monetary policy has before this happens.

Meanwhile, the unemployment rate fell below the Fed’s “natural rate” estimate in December 2016, which should (in theory) intensify upward pressure on prices (see Figure 2). Instead, remarkably weak CPI prints in March and April brought the Fed’s preferred measure of market-based long-term inflation expectations down to 1.9%, around half a percentage point below the Fed’s target in CPI terms (see Figure 3). The April CPI report reflected broad-based weakness across a range of core goods and services, prompting us to revise our 2017 year-end PCE forecast to 1.5%, versus the Federal Open Market Committee (FOMC) median projection of 1.9% and its 2% PCE target.

How low will the NAIRU go?

The natural rate of unemployment is also something of a moving target. Only a few years ago, the NAIRU – which is itself a construct, and thus not directly observable – was considered to be about 6%. But with inflation nowhere to be seen, the Fed gradually lowered it all the way down to 4.7%. Since the NAIRU estimate is derived from a variant of the Phillips curve relationship, it seems logical to acknowledge the risk that it will continue to fall along with the unemployment rate.

This introduces another problem: While everyone accepts that the U.S. economy is closing the unemployment gap, no one really knows how close we are – or what the true natural rate of unemployment actually is.

Key takeaways

Softening inflation calls into question the Fed’s presumed plan to hike interest rates in June, notwithstanding that the unemployment rate has been falling faster than the Fed had originally anticipated. In this context, we think a hawkish bias appears inconsistent with a data-dependent approach.

The Fed has recently maintained that its 2% inflation target is symmetric, but hiking rates when inflation is below target (and slowing) could signal to investors that monetary policy will more likely than not miss the target on the downside. We think pausing here, waiting for inflation to reach 2% and eventually resuming tightening once it can better pinpoint the NAIRU could be a better approach. If inflation expectations continue to lie below the target, this would only undermine the Fed’s credibility in carrying out its price stability mandate, and the market is no longer giving the Fed the benefit of the doubt on this one.

In sum, we believe the Phillips curve framework is doing a poor job at forecasting inflation, even after tweaking the two main inputs: inflation expectations and (to a lesser extent) the NAIRU. Inflation expectations seem to be well anchored, but no one knows where. And the NAIRU could, at least theoretically, drop all the way down to 0% before inflation accelerates meaningfully.

In the meantime, the Fed faces a stark choice: continue to tighten policy preemptively, or listen to what the data and the markets have to say.