Housing starts in December rose a bit more than expected, the US Census Bureau reports, but the modestly upbeat news was marred by the decline in new building permits in last year’s final month. As a result, the overall profile for these leading indicators remains muddled at best. On a year-over-year basis the trend certainly looks sluggish, in contrast with the generally brighter news from other key economic reports in recent months.

But perhaps housing has an ace up its sleeve. The renewed decline in mortgage rates lately is expected to deliver stronger comparisons in the months ahead. In fact, that’s already happening, or so the weekly updates on mortgage applications show for the year so far. New filings jumped a strong 14.3% last week, according to the Mortgage Bankers Association—and the news follows the previous week’s 49% surge. The renewed demand for mortgages implies that we’ll see a stronger run of housing numbers generally in the near term… but not today.

Housing starts rose to a seasonally adjusted annualized rate of 1.089 million units last month, a decent rise from November 1.043 million pace. The gain translates into a year-over-year increase of 5.3%. But as you can see in the chart below, the annual trend in starts has decelerated sharply in recent history, at times dipping into negative territory over the last year. New issued building permits for residential construction looks even weaker, slipping fractionally last month; for the year through December, permits are virtually flat. At best, this chart tells us that housing’s recovery has decelerated by a hefty degree.

The numbers overall look troubling for starts and permits, but there are at least two reasons to wonder if the recent weakness isn’t as dark as it appears. First, as noted, falling mortgage rates may act as a stimulant for housing demand. The national average for the 30-year fixed rate has dropped recently to the mid-3% range, which is the lowest in nearly two years. No doubt this is a factor in the sharp increase in new mortgage applications this month. Given the disinflationary winds blowing globally these days, it’s likely that mortgage rates will stay low if not drop further in the coming weeks.

The fact that US economic growth has picked up lately is a key factor too. The improvement in job growth in particular suggests that any weakness in the housing market is a temporary affair rather than a warning signal for the business cycle. It doesn’t hurt that energy costs have fallen dramatically over the last six months, providing support for household balance sheets.

Some analysts note that despite today’s mixed bag of housing numbers, the single-family unit component is performing better than the general trend, which signals that housing’s outlook is improving. Indeed, new construction for single-family houses jumped 7.2% last month vs. November, substantially faster than the 4.4% monthly gains for starts overall. More importantly, single-family units are ahead by 7.9% on a year-over-year basis through December vs. a 5.3% rise for new residential construction in total.

Is the faster increase in single-family units a reason to remain optimistic on housing? Yes, according to a senior economist at Societe Generale in New York. “The strength is where you’d like to see it, in single-family housing,” Brian Jones tells Bloomberg. “It bodes well for residential real estate. It’s another thing going in the right direction for the economy.”

As usual, however, there’s a joker in the deck and it’s lurking in the global economy–Europe’s weakness and China’s deceleration in particular. So far, the fallout from abroad has had minimal impact on the US economy. But it’s folly to think that the US can remain completely walled off from any troubles abroad. On the short list of risk factors to monitor: the stronger dollar, which is a byproduct of renewed concerns that the rest of the world is facing stronger macro headwinds. As usual, the dollar is perceived as a safe haven. But a rising greenback acts as de facto monetary tightening for the US.

So far, that tightening hasn’t caused much pain, in part because of the offsetting stimulus via falling energy prices. But if there’s a canary in this coalmine, you’ll hear the chirping in the halls of the Federal Reserve. At the moment, it’s still widely assumed that the Fed will start raising interest rates later this year, perhaps as early as June. The motivating factor, of course, is the recent improvement in the US macro trend. But if the central bank delays the timing of the first rate hike, as some analysts now predict, that’ll be a sign that the outlook for the economy isn’t as strong as assumed.

“You have some cracks appearing in the official line that lower oil prices are good for the U.S. economy and that the U.S. can grow even if the global economy is weakening,” advises Thomas Costerg, an economist at Standard Chartered Bank. “There are headwinds.”

There have been all along, of course. The question is whether the marginal change in the headwinds is strengthening for the US trend? It’s still reasonable to answer in the negative. But as today’s housing numbers remind, confidence about the future can still look a bit wobbly depending on the data set under scrutiny.