Economists combine the prices of a variety of goods and services into a single:

1. Many prices must be summarised by one number. 2. Measuring inflation requires a single summary figure. 3. Economists combine prices of a variety of goods and services into a single price level. 4. Changes in that level are what inflation measures. _Source: OpenStax Principles of Macroeconomics for AP Courses 2e (CC BY 4.0), Ch 8 'Inflation'_