Call it the Icarus Effect: Flying higher than anybody sends you crashing back to Earth. That rule seems to apply to Manhattan’s office rents, which are declining more sharply than those in other U.S. markets, though it’s probably due to a soaring multi-year run-up. In the second quarter, average Manhattan asking rents were $60.23 per square foot, down from $71.59 a year ago, or an almost 16 percent plummet, according to Cushman & Wakefield, the commercial brokerage, which analyzed the three sub-markets that make up Manhattan’s central business district: Midtown, Midtown South and Downtown. In contrast, the average price in the second quarter in all U.S. markets together, from Atlanta to Tucson, was $36.70 per square foot, down from $40.19, or a nearly 9 percent drop, the data shows. [more]