Why would the sale of a secondhand car not be included in a calculation of GDP?

The sale of a secondhand car is not included in the calculation of GDP because it does not reflect new production within the economy. Gross Domestic Product measures the total value of all new goods and services produced within a country's borders during a specific time period. When a secondhand car is sold, the production of that vehicle occurred in a previous period when it was originally manufactured. Therefore, counting the sale of the car again would lead to double counting, as the production of that car has already been included in GDP when it was first sold as a new vehicle.

This approach ensures that GDP accurately reflects only the value added to the economy in the current period, which is why considering the production of goods and services that are new is critical for GDP calculations.