The inflation rate was 7.5 percent from January 2021 to January 2022, the highest inflation in 40 years. It arrived suddenly and unexpectedly. A year ago the inflation rate was 1.4 percent, which was lower than the 1.7 percent average rate over the previous decade.

It’s an unwelcome throwback to the Great Inflation of the 1970s. What happened, and when will it go away?