How to measure Gross Domestic Product (GDP)?

The most well-known and frequently tracked metric used for measuring the economic growth of a country is the gross domestic product (GDP). The Gross Domestic Product measures the value of goods and services produced by a nation both for domestic sale and exports. However, GDP does not include imports for measurement, as imports are not produced in the country.
The most accurate measurement of growth is real GDP. The word “real” means that the total has been adjusted to remove the effects of inflation. Generally, there are three different ways to measure the growth of real GDP. They are Quarterly growth at an annual rate, the four-quarter or “year-over-year” growth rate, and the annual average growth rate. The quarterly growth at an annual rate shows the change in real GDP from one quarter to the next, compounded into an annual rate (annualized).
The four-quarter growth rate compares the level of GDP in one quarter to the level of GDP in the same quarter of the previous year. For example, the GDP level of the first quarter of 2019 is compared with the first quarter level of 2018.
The year-over-year growth rate equates with the previous year level of GDP. The year-over-year growth rate tends to be somewhat less volatile than quarterly growth at an annual rate. This is because the effect of any special factors does not get compounded. On the other hand, it is also less timely, since it compares at features of the economy over the entire previous year, not just the past three months. The annual average growth rate is measured through the average of year-over-year percentage changes reported during a year.
However, GDP calculation has its own limitations and biases. It does not include income sent back by Non-Residents working overseas that makes major contribution to growth of emerging economies. It does not include unpaid services like child care, unpaid voluntary work, social programmes etc. It does not include production activities through black money and black market operations. Further, GDP measures only the final production and the parts that are manufactured to make a product not included. It means it does not actually measure relative productivity.