GDP Deflator (Overview, Formula) | How to Calculate GDP Deflator?

What is GDP Deflator?

GDP Deflator (Implicit Price Deflator) is a measure of all price levels for all goods and services within an economy and is used for gauging the effects of inflation on a country’s output. It’s a measure of price inflation/deflation with respect to the specific base year and is not based on a fixed basket of goods or services but is allowed to be modified on a yearly basis depending on consumption and investment patterns.

The GDP deflator of the base year is 100.

Formula of GDP Deflator

The formula of GDP Deflator is as follows –

Where,

Nominal GDP = GDP evaluated using that current market prices
Real GDP = Inflation adjusted measure of all goods and services produced by an economy in a year

How to Calculate GDP Deflator

Here, we have used the following data for the calculation of the GDP Deflator formula.

In the below template, we have calculated the GDP Deflator for the year 2010 using the above-mentioned formula of GDP Deflator.

So, GDP Deflator calculation for the year 2010 will be –

Similarly, we have calculated the GDP Deflator for the year 2011 to 2015.

Therefore, GDP Deflator calculation for all years will be –

It can be noticed that the deflator is decreasing in 2013 and 2014 compared to the base year of 2010. This indicates that the aggregate price levels are smaller in 2013 and 2014 indicating the impact of inflation on GDP, measuring the price of inflation/deflation compared to the base year.

The GDP deflator can also be used to calculate the inflation levels with the below formula:

Inflation = (GDP of Current Year – GDP of Previous Year) / GDP of Previous Year

Extending the above example, we have calculated the inflation for 2011 and 2012.

Inflation for 2011

Inflation for 2011 = [(110.6 – 100)/100] = 10.6%

Inflation for 2012

Inflation for 2012 = [(115.6 – 110.6)/100] = 5%

The results highlight how the general price of all goods and services in the economy falls from 10.6% in 2011 to 5% in 2012.

Importance of GDP Deflator Calculations

Though measures like CPI (Consumer Price Index) or WPI (Wholesale Price Index) are existing, the GDP deflator is a broader concept due to:

It reflects the prices of all domestically produced goods and services in the economy compared to CPI or WPI since they are based on a limited basket of goods and services thereby not representing the entire economy.
It includes prices of investment goods, government services, and exports while excluding prices of imports. WPI, for instance, does not consider the service sector.
Important changes in the consumption patterns or introduction of new goods or services are automatically reflected in the deflator.
WPI or CPI is available on a monthly basis whereas deflator comes with a quarterly or yearly lag after GDP is released. Thus, monthly changes in inflation cannot be tracked which does impact its dynamic usefulness.

Practical Example – GDP Deflator of India

The below graph shows the GDP Deflator of the Indian Economy:

source: Tradingeconomics.com

As it can be seen the GDP deflator is steadily increasing from 2012 and is at 128.80 points for 2018. A deflator above 100 is an indication of price levels being higher as compared to the base year (2012 in this case). It’s not necessary that inflation is occurring but one can experience deflation after a period of inflation if prices are higher compared to base year.

In the above graph, the base year was changed in 2012 to better reflect the economy as it would cover more sectors. Prior to that, the base year was 2004-05 which required to be changed.
Since India is a rapidly growing economy with dynamic changes to its policy the mentioned changes were essential. Also, the increasing deflator reflects a steady increase in inflation due to continuous growth opportunities.
As per World Bank Reports for 2017, India ranks 107 for the list of GDP Deflator with an inflation rate of 3%. This can be stated as a comfortable position compared to countries which may be facing hyperinflation such as South Sudan and Somalia. On the contrary, it also does not face the threat of deflation such as Aruba and Liechtenstein. Hence, it is important to keep it at manageable levels.
The RBI has adopted the CPI as a nominal inflation anchor because, during 2016, the GDP Deflator suggested the country entering a deflation zone while CPI continuing to exhibit a moderately high inflation level. Such situations can push the economy into deflation with the implication being that corporate earnings and debt servicing ability which closely tracks Nominal GDP will keep on deteriorating while inflation-adjusted GDP (Real GDP) may continue to exhibit growth rate in excess of 7%.

GDP Deflator vs CPI (Consumer Price Index)

Despite the presence of GDP Deflator, the CPI seems to be the preferred tool used by economies for ascertaining the impact of inflation in the country. Let us look at some of the critical differences between GDP Deflator vs CPI

GDP Deflator		CPI (Consumer Price Index)
Reflect the price of all goods and services domestically produced		Reflects the price of goods and services ultimately purchased by the final consumers
It compares the price of existing produced goods and services against the price of the same goods and services in the base year. This makes the group of goods and services used for GDP computation change automatically over time.		It compares the price of the fixed basket of goods and services to the price of a basket in the base year.
It contains prices of domestic goods		Imported goods are also included in the same.
For instance, in the Indian economy, the price change of oil products is not reflected much in the GDP deflator since domestic oil production is low in India.		As most of oil/petroleum is imported from Western Asia, whenever the price of oil/petroleum product changes, it is reflected in CPI basket as petroleum products compute larger share within CPI.
Another example can be of ISRO satellite which shall be reflected in the deflator.		Assuming the price of ISRO increases, it would not be a part of CPI index as the country does not consume satellite.
It assigns changing weights over time as a composition of GDP changes.		Assigns fixed weights to prices of different goods. It’s computed using a fixed basket of goods.

GDP Deflator