pricing Carbon pricing is being implemented by governments to reduce the use of carbon fuels. Carbon pricing can be determined by specific policies such as taxes or caps or by commitments such as emission reduction commitments or price commitments. However, emission reduction commitments (used by the Kyoto Protocol) can be met by non-price policies, so they do not necessarily determine a carbon price. Carbon policies can be either price-based (taxes) or quantity-based (cap and trade). A cap-and-trade system is quantity-based because the regulator sets an emissions quantity cap and the market determines the carbon price. The IMF’s Fact Sheet states that “Cap-and-trade systems are another option, but generally they should be designed to look like taxes through revenue-raising and price stability provisions." Such designs are often referred to as hybrid designs. The stability provisions referred to are typically floor and ceiling prices (a ceiling price is also known as a safety valve), which are implemented as follows. When permits are auctioned, there is a floor (reserve) price below which permits are not sold, and permits for immediate use are always made available at the ceiling price, even if sales have already reached the permit cap. To the extent the price is controlled by these limits, it is a tax. So if the floor is set equal to the ceiling, cap-and-trade becomes a pure carbon tax. US airfare before 1978 Until the late 1970s, government regulated price floors on airfares in the US made flying "absurdly expensive" to the point that in 1965, more than 80% of Americans had never flown on a jet. For example, in 1974, US air carriers had to charge at least $1,442 (in inflation-adjusted dollars) for a New York City to Los Angeles trip, a flight that cost as little as $278 in 2013. In 1978, the US government deregulated airfares, on the grounds that flying is not a necessity (like food or prescription drugs), and nor was it addictive (like alcohol). The government deregulated airfares so that increased competition would lead to a drop in airfare prices. By 2011, the inflation-adjusted cost of air travel dropped by half as compared with 1978. By 2000, half of Americans were taking at least one round-trip air flight per year. Private sector While the setting of price floors is often associated with government measures, there are also private sector-imposed price floors. Until November 2016, the National Football League