GDP Deflator
In economics, the GDP deflator (implicit price deflator for GDP) is a measure of the level of prices of all new, domestically produced, final goods and services in an economy. GDP stands for gross domestic product, the total value of all final goods and services produced within that economy during a specified period.
In most systems of national accounts the GDP deflator measures the ratio of nominal (or current-price) GDP to the real (or chain volume) measure of GDP. The formula used to calculate the deflator is:
Dividing the nominal GDP by the GDP deflator and multiplying it by 100 would then give the figure for real GDP, hence deflating the nominal GDP into a real measure.
It is often useful to consider implicit price deflators for certain subcategories of GDP, such as computer hardware. In this case, it is useful to think of the price deflator as the ratio of the current-year price of a good to its price in some base year. The price in the base year is normalized to 100. For example, for computer hardware, we could define a "unit" to be a computer with a specific level of processing power, memory, hard drive space and so on.
A price deflator of 200 means that the current-year price of this computing power is twice its base-year price - price inflation. A price deflator of 50 means that the current-year price is half the base year price - price deflation.
Unlike some price indexes, the GDP deflator is not based on a fixed basket of goods and services. The basket is allowed to change with people's consumption and investment patterns. (Specifically, for GDP, the "basket" in each year is the set of all goods that were produced domestically, weighted by the market value of the total consumption of each good.) Therefore, new expenditure patterns are allowed to show up in the deflator as people respond to changing prices. The advantage of this approach is that the GDP deflator reflects up to date expenditure patterns. For instance, if the price of chicken increases relative to the price of beef, people would likely spend more money on beef as a substitute for chicken. A fixed market basket measurement would miss this change.
In practice, the difference between the deflator and a price index like the Consumer price index (CPI) is often relatively small. On the other hand, with governments in developed countries increasingly utilizing price indexes for everything from fiscal and monetary planning to payments to social program recipients, the even small differences between inflation measures can shift budget revenues and expenses by millions or billions of dollars.
Price Index
A price index (plural: “price indices” or “price indexes”) is a normalized average (typically a weighted average) of prices for a given class of goods or services in a given region, during a given interval of time. It is a statistic designed to help to compare how these prices, taken as a whole, differ between time periods or geographical locations.
Price indices have several potential uses. For particularly broad indices, the index can be said to measure the economy's price level or a cost of living. More narrow price indices can help producers with business plans and pricing. Sometimes, they can be useful in helping to guide investment.
No clear consensus has emerged on who created the first price index. The earliest reported research in this area came from Welshman Rice Vaughan who examined price level change in his 1675 book A Discourse of Coin and Coinage. Vaughan wanted to separate the inflationary impact of the influx of precious metals brought by Spain from the New World from the effect due to currency debasement. Vaughan compared labor statutes from his own time to statutes dating back to Edward III. These statutes set wages for certain tasks and provided a good record of the change in wage levels.Vaughan reasoned that the market for basic labor did not fluctuate much with time and that a basic laborers salary would probably buy the same amount of goods in different time periods, so that a laborer's salary acted as a basket of goods. Vaughan's analysis indicated that price levels in England had risen six to eightfold over the preceding century.