The Joint Center for Housing Studies of Harvard University has published its new “State of the Nation’s Housing 2011″ report, which shows rental vacancy rates are declining, rents are increasing and low-cost rental units are fast disappearing. The report found that demand climbed to 18 million from 16.3 million of renters with very low incomes from 2003 through 2009. Meanwhile, available units fell to 11.6 million from 12 million. Read more…