>8 The Data of Macroeconomics CPI may overstate inflation Consumers may substitute away from more expensive goods e.g. 1978-1981US price rose 9. 1%o per year according to the gdp deflator; according to CPl, price rose 11.2%o per year. Why?The Data of Macroeconomics CPI may overstate inflation Consumers may substitute away from more expensive goods. e.g. 1978-1981 U.S. price rose 9.1% per year according to the GDP deflator; according to CPI, price rose 11.2% per year. Why?