Since 2006, economist and former Bush-era White House adviser Greg Mankiw has been encouraging economists and policy makers to join the Pigou Club, which advocates for a tax on carbon. The idea goes back to economist Arthur Cecil Pigou, who, in 1920, proposed to tax market activities that generate externalities—costs that are not included in a product's market price, such as the healthcare costs of using tobacco. In the case of carbon, such a tax would raise revenue for the government while making sure those who choose to burn fossil fuels (say, when you drive your car to work) adequately take into account that choice's damage to the environment and the health and safety of others.