Using annual data since 1956, create scatter plots of the following variables:

a. CPI inflation rate (December to December) against the average unemployment rate for the year.

b. CPI inflation rate against the cyclical unemployment rate. (The cyclical unemployment rate is the actual unemployment rate minus the natural unemployment rate, which is variable \(N R O U\) in the FRED database.)

c. Change in the CPI inflation rate from the previous year against the cyclical unemployment rate. Discuss your results in light of the theory of the Phillips curve.