Today’s update on September consumer price inflation suggests that the worries about deflation in recent months weren’t misguided. Although consumer prices overall are still rising, the increase is slight. More worrisome is the trend. The annual pace of consumer inflation continues to fade. It’s not a rapid decline, although it’s fairly persistent. Given the macroeconomic backdrop these days (lots of debt and sluggish growth hobbling the economy and labor market), the disinflation trend can’t be dismissed. Until and unless it’s stopped, we know how this movie ends, and it’s not going to be pretty. Fortunately, the central bank still has the power to alter the outcome, but the clock is ticking.

Last month, the consumer price index (CPI) rose a bare 0.1%, the U.S. Labor Department reported—down from 0.3% in August. This could be statistical noise, of course, which inspires looking at the longer-term trend in terms of rolling 12-month percentage changes. By that measure, a picture of what’s been happening speaks for itself. As the chart below illustrates, the rate of increase in headline consumer inflation has been slipping for most of this year. Through September, CPI rose 1.1% vs. a year earlier, down from a 2.7% annual pace in January.

The Federal Reserve and many economists prefer to look at consumer inflation on a “core” basis, which means stripping out food and energy prices. Those two factors can distort the numbers in the short term for various reasons. In fact, a number of studies have shown that over time, core CPI is a better indicator of where inflation overall is headed. At the very least, the trend in core CPI is worth watching, if only for additional perspective. On that front, however, the news isn’t any better relative to headline CPI. In fact, one can argue that the trend in core CPI is quite a bit worse when it comes to worrying about the risk of future deflation.

Consider the second chart below, which graphs the annual 12-month percentage change in core CPI. Last month, core CPI rose by 0.8% on a year-over-year basis. That’s the lowest rate so far this year. In fact, it’s the lowest 12-month percentage change since the early 1960s. If you’re looking for reasons to worry that inflation is an imminent threat, you won’t find it here.

The issue isn’t whether low inflation is inherently bad. It’s not. But the risk isn’t that inflation stays low, which would be a good thing. Rather, the worry is that the disinflationary trend rolls on, eventually turning into deflation.

Some critics of the Fed’s apparent willingness to embrace a new round of quantitative easing complain that the central bank is fostering the seeds of higher inflation. If so, there’s little if any evidence in support of that fear in today’s CPI report. Don’t misunderstand: the methodology behind the CPI calculation is flawed. But it’s not so flawed that the general trend it depicts is erroneous.

In fact, independent measures of broad inflation from various economic shops more or less corroborate the broad trend that’s apparent in CPI. There’s plenty of room for debating the details, but on the fundamental issue of whether inflation is rising, remaining stable, or decelerating, the evidence looks fairly convincing that the latter condition prevails these days.

What’s the solution? Ultimately, the Fed must stabilize the disinflation trend, in large part by stabilizing inflation expectations. That requires convincing the crowd that the central bank is serious about raising inflation’s pace. As I discussed earlier this week, there’s been some recent evidence in the markets for thinking that the Fed has made some progress with that goal. But today’s CPI report reminds that the battle to beat the D risk out of the system isn’t quite over. In fact, it’s unclear if the real war is just beginning.

Yes, inflation will one day return as the priority in monetary policy, and the Fed must act accordingly when that turning point arrives. But first things first.