# When Calculating Price Indices Like the GDP Deflator and the CPI We Multiply the Ratio by 100. Why?

When Calculating Price Indices Like the GDP Deflator and the CPI We Multiply the Ratio by 100. Why?

Price indices play a crucial role in measuring the changes in prices of goods and services over time. Two commonly used price indices are the GDP deflator and the Consumer Price Index (CPI). These indices are calculated by multiplying the ratio of current prices to base prices by 100. This article aims to explain why this multiplication by 100 is necessary, along with addressing 12 frequently asked questions related to price indices.

Why Multiply by 100?
The primary reason for multiplying the ratio by 100 is to express the resulting value as a percentage. This allows for easier interpretation and comparison of the price changes. By multiplying the ratio by 100, it converts the decimal value into a percentage, making it more intuitive for users to understand.

1. What is a price index?
A price index is a statistical measure that tracks the changes in the prices of goods and services over time, providing insights into inflation or deflation.

2. What is the GDP deflator?
The GDP deflator is a price index that measures the overall price level of all final goods and services produced within an economy.

3. What is the CPI?
The Consumer Price Index (CPI) is a price index that measures the average price level of a basket of goods and services typically consumed by households.

4. How are price indices calculated?
Price indices are calculated by dividing the current price of a basket of goods or services by the base price and multiplying the result by 100.

5. What is the base year in price indices?
The base year is the reference year against which the current prices are compared. It is assigned an index value of 100.

6. Why is the base year important?
The base year provides a benchmark against which price changes can be measured. It allows for comparisons and analysis of price movements over time.

7. What does an index value above 100 indicate?
An index value above 100 indicates that prices have increased compared to the base year, reflecting inflation.

8. What does an index value below 100 indicate?
An index value below 100 indicates that prices have decreased compared to the base year, reflecting deflation.

9. How are price indices used?
Price indices are used to track inflation, adjust wages and pensions, assess changes in purchasing power, and make economic policy decisions.

10. Can price indices be used to compare prices over different countries?
Yes, price indices can be used to compare prices between countries. However, caution must be exercised due to differences in consumption patterns and quality of goods and services.

11. Can the GDP deflator and CPI be used interchangeably?
No, the GDP deflator and CPI serve different purposes. The GDP deflator measures price changes of all goods and services produced, while the CPI specifically focuses on goods and services consumed by households.

12. Are price indices perfect measures of inflation?
Price indices serve as proxies for measuring inflation, but they may not capture all aspects of price changes accurately. Factors like quality improvements and changes in consumption patterns can impact the accuracy of price indices.