The first half of the year has proven the U.S. office game is still strong, but 2015's banner year will be hard to beat. The volume of office sales completed in the first half of 2016 has dipped compared to the same time last year, according to early CoStar data. Hans Nordby, managing director for CoStar Portfolio Strategy, labeled this latest statistic "a worry" because a drop in transaction volume "generally portends a decrease or at least a flattening in prices."