Tenants have reclaimed an advantage, albeit a very slight or symbolic one, over landlords in O'ahu's office market.

Two local commercial real estate firms said vacancy rates in the first half of this year rose above 10 percent, the point at which negotiating positions of landlords and tenants generally are balanced.

During the past four years, landlords enjoyed the upper hand with relatively low vacancies and strong tenant demand that enabled them to raise rental rates. But the recession has changed that, and is presenting more attractive opportunities for businesses seeking to lease office space.

Colliers Monroe Friedlander in a recent report said the rough equivalent of a 20-story building — 209,850 square feet of office space — was vacated on O'ahu during the first half of this year, including 122,300 square feet in the second quarter.

That pushed the vacancy rate to 10.2 percent, up from 8.6 percent at the end of the year, according to Colliers.

A similar survey by rival firm CB Richard Ellis put the mid-year vacancy rate at 10.1 percent.

Technically, tenants have the slightest of edges for negotiating an office space lease, though based on the equilibrium point of 10 percent vacancy the market is roughly balanced.

Colliers in its report said landlords are lowering asking rents, and that tenants are obtaining rents below asking rates. However, Colliers also said some terms on new negotiated leases are including annual increases of 3 percent or more with little or no landlord concessions.

"It does not appear that negotiations have been more favorable to one party over the other," Colliers said in its report.

Colliers predicts that O'ahu's office vacancy will continue to decline due to rising unemployment and the weak economy, pushing the vacancy rate to somewhere between 10.6 percent and 11 percent by the end of the year.

CB Richard Ellis noted one expected bright spot in the federal government's plan to lease commercial office space during a planned renovation of the 930,000-square-foot Prince Kuhio Federal Building Downtown, though the timing and magnitude of the temporary relocation of federal office workers was unclear.

In its report, CB Richard Ellis said it expects vacancies to drop, but its survey counted significantly fewer vacancies in the first half of this year compared with the Colliers report.

The CB Richard Ellis survey reported 124,350 square feet of vacant space was added to the market in the first half of this year, including a reduction, or filling, of 6,846 square feet in the second quarter. The firm surveys 100 buildings with a total of 11.5 million square feet of rentable area in the two highest classes of property.

The Colliers survey covers 163 buildings in three classes representing 15.7 million square feet of rentable space.