Data on the median age of the U.S. population in selected years are listed in the table below. Model the data with a linear function, estimate the median age in 1998, and predict the median age in 2020. Answers may vary depending on the data points used.
Year, x Total U.S. Expenditures
1970, 0 ............................ 28.0
1980, 10 ......................... 30.0
1990, 20 ......................... 32.8
2000, 30 ......................... 35.3
2008, 38 .......................... 36.8
2011, 41 .......................... 36.9*