Simon Kuznets was the first economist to create the first true GDP estimate, which he delivered to the United States’ Congress in 1934. Since then, government statistical offices all around the world have been producing GDP estimates.
Three methods are used to arrive at these estimates. First is to add up all the money spent in the year. Second is to add up all the money earned in the year. And third is to add up all the value added in the year. Some countries, such as the United Kingdom, combine all three methods into a single GDP number, whereas the United States uses only the spending figure to estimate the GDP.
China, meanwhile, calculates gross domestic product after taking into account three factors: production, income and expenditure.