CBRE's report put Q2 net absorption at minus 929,000 square feet, approximately the same as Q1, pushing the mid-year total to minus-1.8 million square feet. The full-year total for 2008 was 2.1 million square feet.

The bulk of the negative net absorption was due to a couple of large leaseholds that had been on the sublease market but expired in the second quarter, according to CBRE, namely the 375,000 square-foot Charles Schwab space at 1 Montgomery, and a 154,816 square-foot Macy's space at 22 4th St.

At first blush the CBRE data seems at odds with Colliers International. Colliers, which tracks 82.8 million square feet, pegs the overall availability rate 600 basis points lower at 14.1%, which is 60 points below CBRE's estimation of the direct vacancy rate. Colliers' report estimated net absorption at minus 688,512, pushing the year-to-date total to minus 1.2 million square feet.

So what gives? Much of the difference can be explained by how each company deals with sublease space. Colliers says it doesn't add sublease space to its calculations until the sublessor vacates the space while CBRE includes the square footage when the space first comes to market.