Surging demand and strong occupancy in the nation’s apartment market is “surprising” experts who say the continued strength is “unexpected.” Just a year ago, there was concern that the rental apartment market was overheated and overbuilt. But now apartment absorption, which is the rate at new units are rented out, is at the highest level in three years, according to the U.S. Census. Meanwhile, home sales were thwarted by tight supply and higher prices and mortgage rates.