The office vacancy rate in Calgary's core has dipped a little in the past three months of 2018 — but optimism may be premature, a new report suggests.

Downtown office vacancies stood at 24.7 per cent in the fourth quarter of 2018, Avison Young reported, down slightly from the 26 per cent rate in the same quarter the previous year, but closer to the 23.9 per cent in the last three months of 2016.

Calgary office vacancies as a whole sat at 22.3 per cent in the fourth quarter of 2018.

"Positive absorption recorded in the last quarter of 2018 helped push annual absorption in Calgary's overall office market into positive territory for the first time in four years," the company said in a release.

But optimism should be tempered.

"While it is great to see the direction change from the multi-million-square-foot-negative-absorption years of 2015 and 2016, the increase has not been material enough to instill the confidence needed to boost the outlook in Calgary," said Todd Throndson, principal and managing director of the company's Calgary office.

Nexen's relocation to The Bow tower and Canadian Tire's move to Quarry Park were two of the biggest real estate stories in the quarter, Throndson said.

Highest rates ever could be around the corner

That vacancy rate, however, could shoot up.

The addition of Telus Sky space in the first quarter of 2019 and speculated energy layoffs could "potentially [lead] to the highest vacancy rates ever recorded in the city," the company said.

And size seems to be shifting too.

"Large tenants are no longer the dominant force in Calgary's office leasing market. On the whole, the average office tenant has shrunk in size. The lion's share of deals being completed today involve tenants smaller than 10,000 square feet."