A softer gain in hiring was expected for December, but today’s report from the US Labor Department was weaker than economists forecast. Companies added 139,000 workers last month–moderately lower vs. the 150,000 consensus point forecast via Econoday.com. That’s still a respectable gain, although it’s no match for November’s blowout surge of 243,000 new jobs in the private sector.

Month-to-month comparisons are unfair generally. A better measure is the one-year change, which slipped to 1.5% in December for the first time since 2011. That, too, is a healthy gain, but it’s clear that the downshift in the trend is ongoing and so 2020’s labor market may look increasingly wobbly in the months ahead if the downside momentum rolls on. Given recent history, that’s a reasonable guess.

For the moment, however, the decelerating growth rate is easy to miss. December’s 1.5% year-over-year gain is nearly indistinguishable from November’s 1.6% increase. But as the chart below reminds, the labor market’s growth rate has been slowing almost non-stop for a year. The good news: it’s a gradual slowdown. Unfortunately, it appears to be persistent.

The next several months will be critical for deciding if it’s time to worry. If growth slips further, falling below 1.5% for more than a month, the implications for the economy will be troubling for some point in the near-term future. A drop below 1.0% would almost certainly signal a recession.

For now, however, a 1.5% annual gain will keep the economy bubbling. Optimists note that a similar episode of slowing employment growth unfolded in 2015-2017, only to rebound in early 2018. Expecting a repeat performance, however, suffers long odds – for several reasons, including ongoing uncertainty of the US-China trade conflict and various geopolitical risks.

Another factor: the outlook for economic growth generally is moderate, at least for now. The fourth-quarter GDP report that’s due later this month, for example, is expected to post a 1.8% gain, based on the median nowcast for several models.

A more reasonable scenario for optimism is a labor market trend that stabilizes, or slips further by the smallest of increments and thereby extends the expansion beyond the shelf life that gloomier projections assume.

Meantime, the slippage is sufficiently measured to keep the cheery observations alive. “There is nothing here that changes the picture of an economy that is continuing to expand at a pace that exceeds its potential growth rate,” advises Conrad DeQuadros, senior economic advisor at Brean Capital. “The Fed should be very comfortable with this report.”

Agreed. But an attitude adjustment is lurking if the 1.5% annual pace in employment growth gives way in the months ahead.