Remodeling contractors should aim their marketing efforts at middle-aged families who have recently had a baby. That's just one of the deductions readers can make from "Improving America's Housing," a recent study conducted by the Joint Center for Housing Studies at Harvard University. Without collecting any original data, researchers analyzed existing sources — most important were the 1993 and 1995 American Housing Surveys from the U.S. Dept. of Housing and Urban Development — to reach conclusions on the size, nature, and future of the remodeling industry. Remodelers making long-term business plans will find some useful statistics: Over 75% of homeowners who have had a child within the past two