“The median listed price for a house jumped 24% in January from a year earlier in the metropolitan area surrounding Allentown, the Rust-Belt city whose decline was memorialized in a 1982 Billy Joel song, according to data from Realtor.com. It was the same in such spots as Martin, Tenn., a small city 150 miles from Nashville, where the median asking price went up 159% over the same period; in Kendallville, Ind., about 30 miles outside Fort Wayne, it climbed 56%.”