With Canada putting in its best six-month jobs performance in 15 years and on track for its best 12-month period on record, there's a lot to be optimistic about in Canada's job market.

The country's unemployment rate dipped to 6.8 per cent last month as the economy added 48,000 jobs, Statistics Canada reported Friday.

But that doesn't mean there's no reason for concern.

Here are four of the main worries of some of Canada's top economists.

The types of job

While job gains were pretty broad-based overall last month, some of the sectors that were shut out of the festivities are concerning.

Take manufacturing, always a key because it tends to spill over into other areas. Employment in manufacturing declined by 7,500 jobs in January, and is down 2.2 per cent in the past year and remains close to all-time lows, BMO economist Doug Porter says.

The Bank of Canada has singled out exports as being key to Canada's long-term recovery, so for such a key export sector to be still lagging is troubling.

Another sector, information, culture and recreation, also lost 12,500 jobs during the month, which is further reason for concern. As BMO's Porter put it, the industry breakdowns are "sounding a bit of a sour note on the proceedings."

They're mainly part-time

As has been the case for several months in a row, growth in part-time jobs outpaced full-time ones in January by more than two to one.

Obviously any job is good news — "a part-time job is better than no job at all," as Manulife's senior economist Frances Donald says — but when the work force as a whole is moving toward part-time, that's bad news for everyone.

Consider that the share of part-time work has been ticking higher since the end of 2015, and rose a full percentage point to almost one out of every five jobs last month, IIHS economist Arlene Kish notes. "The shift to part-time employment," she says, "can stretch consumers and further contribute to household imbalances."

They're paying less

That's because, all things being equal, part-time work pays less than full time. Statistics Canada's latest numbers show that across all salaried workers, average hourly wages were only one per cent higher in January than in the same month a year ago. That's the smallest annual gain since 2003, Dominion Lending Centres chief economist Sherry Cooper notes.

Factor in inflation, and that means workers are actually worse off today than they were a year ago in terms of purchasing power.

"All of these bodies getting jobs are being hired at slowing wage growth," Scotiabank's Derek Holt says, "which dents the income and spending implications."

There's less actual work being done

With the influx of part-time workers, it's perhaps not surprising to learn that the number of total hours worked is also inching downward. But the reality of the numbers is actually quite shocking.

Hours worked dipped by 0.5 per cent in absolute terms in January compared to December. That may not sound like an alarming figure, but zoom out a little and consider that there was 0.8 less paid work being done last month than there was a year ago. "It wasn't even that bad in the depth of the oil crisis," Donald says.

Considering the economy added 276,000 new workers over that time period, that's astounding. "More bodies working fewer hours seems to be the trend of late and for quite some time," Holt says. "At some point employers might slow their pace of adding more bodies and demand more from the existing ones they've added."

Bonus: Good news can lead to bad

While few expect the Bank of Canada to move any time soon, a few more months of sizzling job numbers might convince the central bank that the economy is ready for higher interest rates. That would be bad news for the millions of Canadians weighed down by record high debt loads.

One of the immediate impacts of Friday's job report was a surge in the loonie, which gained more than a third of a cent to 76.40 cents US. A strong loonie sounds like great news for Canadians who travel abroad, but it's terrible news for exporters, who prefer a weak dollar to make their products more attractive internationally.

As Holt put it: "Backward-looking job growth is great, but not if Canada winds up suffering a negative shock to trade," because of it.