consider the following data on u.s. gdp: year gdp (billions of current dollars) (billions of 2012 dollars) 2014 17,521.7 16,899.8 2015 18,219.3 17,386.7 2016 18,707.2 17,659.2 2017 19,485.4 18,050.7 2018 20,494.1 18,566.4