Deflation occurs when there is a decrease in the general price level of goods and services, which is indicated by a negative change in the Consumer Price Index (CPI).
In the table provided:
- Year 1: +2%
- Year 2: +3%
- Year 3: +1%
- Year 4: -4%
The only year with a negative percentage change in the CPI is Year 4, where the change is -4%.
Therefore, the economy experienced deflation in Year 4.