What is the common relationship between RPI and CPI during inflationary periods?

During inflationary periods, the Retail Price Index (RPI) often reflects a higher measure of inflation compared to the Consumer Price Index (CPI). This difference arises because RPI includes a wider range of costs, such as housing costs, like mortgage interest payments and property taxes, which can significantly impact the overall index during periods of rising prices. Additionally, RPI accounts for certain benefits and allowances that can further increase its value during inflation.

CPI focuses more on the prices of a basket of goods and services consumed by households and does not include housing costs in the same way that RPI does. As a result, during inflationary periods, it is common to observe RPI registering a higher inflationary effect due to these additional components it measures. This characteristic makes RPI a more encompassing measure of the cost of living when housing costs are volatile, thus justifying the assertion that RPI is generally higher than CPI during inflationary phases.