The article introduces a new way to measure changes in the prices of goods and services in different European countries. By looking at consumer prices and exchange rates, the researchers studied how the prices in the European Union changed from 1991 to 2002. They found that comparing prices between countries can be tricky, leading to different methods being used to make accurate comparisons. The study focused on understanding how the prices in different countries affect each other and how this can impact their economies. The researchers defined an index to show changes in the relative purchasing power of these countries, even if they don't use the same currency.