Instead of using the total population, we might deflate cigarette sales by the number of people over the age of 18, since a person must be at least 18 years old to buy cigarettes legally. There were 116 million people over the age of 18 in the United States in 1960 and 186 million in 1990. Use the data in the text to calculate the percentage change between 1960 and 1990 in cigarette consumption per person over the age of 18.