"The numbers are big," RBJ director of research Brendan Carroll tells GlobeSt.com, with 1.6 million sf of positive absorption between April and mid-year. That marks the sixth straight quarter of positive absorption, and the 5.1 million sf absorbed since halfway through 2006 is the most for any such period since 2001. "The metrics look good just about everywhere," says Carroll, whose Boston-based firm tracked 630,000 sf of positive absorption in the city during the quarter, with 315,000-sf of that occurring in the Back Bay District, now among the strongest office markets in the country.

Besides the standard mid-year review, RBJ issued a special look dissecting office market trends since conditions began improving four years ago after the brutal recession that started the decade. Since the third quarter of 2003, a limited number of submarkets have enjoyed the lion's share of leasing activity and rental rate gains, discloses RBJ, which refers to the top performers as the "hot markets." They include Class A space in Boston's Financial District and Back Bay, plus all categories of office product in East Cambridge, Burlington, Waltham and Woburn.

Collectively, the hot markets account for 60.2 million sf, compared to 111 million sf in the remaining areas. Since Q3 2003, the hot markets have seen their vacancy rate decline from 21.1% to 9.6%, whereas the larger pool has only experienced a dip from 19.6% to 16.8%. That means 69% of all leasing in metropolitan Boston has been done in the "hot markets," says Carroll, which account for just 35% of the inventory. There has been 8.4 million sf of absorption since 2003 in the hot markets versus 4.5 million sf for the remainder.