When considering a country’s fair share, we have to ask how much of the global problem it is responsible for. One key challenge here is choosing the year when national emissions should start counting towards historical responsibility. Should it be 1850, a year that predates most all industrial activity? In 1950, when the great global economic boom began in earnest? In 1990, when our governments were drafting the UN Framework Convention on Climate Change? In our analysis, we use 1950, while acknowledging that this is somewhat generous towards the United States since it discounts all of our emissions before that date.