LAS VEGAS There are 6 million empty homes in the United States. Or 6.2 million, to be slightly more precise. Empty houses are normal to some extent -- part of the usual friction of building, selling, renting. But ask the people who study the numbers, and who understand the "overhang" in housing inventory, and they'll tell you: This country has about a million homes too many. The solution, local executives say, will come not from Washington policymakers but from the market itself. When there are too many houses, builders stop building them. That has already happened, and many Vegas home...