Too Many Vacant Lots, Not Enough Housing: The U.S. Real-Estate Puzzle

DaJuan Robinson was remodeling a house on the South Side, not far from the University of Chicago, when he spotted a vacant lot two doors away. He thought it might be worth developing.

Then he learned about the back taxes, unpaid water bills and other hurdles that would take too much time and money to clear. That was seven years ago. In March, he sold a triplex he had built on an empty lot nearby for $815,000, benefiting from county initiatives intended to encourage new housing on miles of blocks...