By the end of 1996 the rate was 16.4 percent, down from 19.4 percent the year before, according to Cushman & Wakefield, the national brokerage.

NEARLY a million square feet of space in eight buildings are under construction along that corridor, according to Cushman & Wakefield, the national commercial brokerage.

Stephen Jenco, senior research analyst at Grubb & Ellis, another national commercial brokerage, is not so sure.

Cushman & Wakefield, the national brokerage, put the corridor's vacancy rate at 10 percent, down from 13.3 percent last year.

Subleases represent 17.4 percent of the overall available office space in the state today, according to Cushman & Wakefield, another national brokerage.

In the last 22 months, 15 buildings totaling 2.2 million square feet have been completed, are under way or about to start, according to Cushman & Wakefield, the national brokerage.

Cushman & Wakefield, the national brokerage, represented AT&T in the transaction.

At $4.43 a square foot, average asking rents remain healthy, according to Cushman & Wakefield, the national brokerage.

So far this year 19 buildings, totaling 4.5 million square feet, have been sold for a total of $440 million, according to Cushman & Wakefield, another national commercial brokerage.

Con Ed and its adviser, Cushman & Wakefield, the national commercial brokerage, first offered for sale three parcels along First Avenue.