Consumers decide what to buy based on price, and the price elasticity of demand measures how much the quantity demanded changes with a change in price. For U.S. domestic air travel, the demand has been less responsive to price changes since the 1970s than previously thought. This means that when prices go down, the increase in passengers is not as high as expected. The researchers used a regression model to analyze factors like price, the economy, and consumer confidence to show that the demand for air travel is not as elastic as believed. This finding challenges the common belief that lower prices lead to more people flying, and suggests that other factors also play a role in determining air travel demand.