Ten states in the Northeast and Mid-Atlantic (see below for the participating states) have taken the lead nationally in promoting cleaner energy and reducing air pollution.  The Regional Greenhouse Gas Initiative (RGGI), begun in 2009, is a multi-state program to reduce carbon pollution and other greenhouse gases from major power plants.  This successful market-based program works by requiring these pollution sources to buy emission “allowances” –a kind of permit--to emit carbon dioxide, and there are only so many “allowances” available in the 10-state region.  Each participating state holds a “share” of these allowances, and revenues from the sale of allowances are reinvested by each state in energy-efficiency programs and other measures to reduce emissions.  As of the end of 2011, RGGI has raised more than $778 million for state reinvestments, including $390 million dedicated to energy efficiency alone.