NEW YORK CITY—The US economy continues to gather steam and hiring continues to pick up, judging by monthly reports from both the federal government and commercial real estate services firms. The employment growth is especially evident in office-using sectors. In spite of this, the decline in the office availability rate has slowed down, says Savills Studley.

After dropping from 17.35 to 16.5% over the course of 2014, the office availability rate has contracted by just 10 basis points so far this year. The nation's top 23 markets recorded 98.8 million square feet of leases as of this past June 30, compared to 115.3 million square feet in the first half of '14.

"Availability has barely budged so far in 2015 as new construction expands in more markets and leasing slows,” says Keith DeCoster, director of US real estate analytics at Savills Studley. “Deal volume in the first half of 2015 has fallen by more than 10% compared to the first half of '14 in most major markets, with very sharp decreases in Boston, Manhattan, Atlanta and Dallas.”

In some markets, a slowdown was probably to be expected. The pullback in the energy sector, for example, provides a ready explanation for the slowdown in Houston, where the availability rate rose from 18.4% to 21.7% over the past year. More surprising, says Savills Studley, is decreased demand in markets that registered strong leasing in '14.

“Some drop-off in the fastest-growing markets like Dallas/Fort Worth was inevitable – there are only so many 500,000-square-foot tenants looking for space, after all,” according to Savills Studley's second-quarter national report. And amid very strong demand from the biopharmaceutical sector in Cambridge, tenants in the Boston region leased only 21.8 million square feet in the past four quarters, down by 17.6% from a year ago. In contrast to these markets, “leasing in Denver, Phoenix, Los Angeles and San Francisco and Silicon Valley shows little sign of cooling.”

In those markets where it has cooled, Savills Studley sees multiple factors in play. For one thing, the company says, “the breakneck pace of job creation in high-growth markets such as Atlanta and Dallas/Forth Worth has decelerated just a bit,” even as it remains above the national average.

Also, according to the report, “the surge in 2006 and 2007 leasing created a cyclical peak in 2016 and 2017 rollovers, which was boosted by companies signing early renewals. The very largest of the tenants in this cohort have satisfied their space needs.”

Addiitonally, “many of the very best bargains were spoken for” in 2013 and last year. “In Lower Manhattan, for example, the sub-$45 class A space that was still out there a few quarters ago has been snared.”

Savills Studley also sees “a bit of a standoff” on asking rents emerging between tenants and owners in markets that are still dominated by traditional space users—Manhattan, Boston, Los Angeles and Chicago, for example. “Biotech companies in Cambridge may be willing to pay $70 or even $80, but banks and law firms are not,” according to the report.

Banks and law firms, the report says, “remain firmly rooted in the reality that their profit margins and revenues are still below pre-recession norms. Consequently, resistance to rental rate escalation in Boston's Back Bay, Downtown Chicago and Midtown Manhattan still prevails.”

Nonetheless, asking rents have increased nationally in each of the past 15 quarters, according to Savills Studley. It remains to be seen, the firm says, “whether this slowdown in leasing is just a lull, or if the concern expressed by some analysts—that the recovery is getting long in the tooth – is becoming a reality.”