National output is measured by what metric?

The measurement of national output is most accurately represented by Gross Domestic Product (GDP). GDP quantifies the total economic output of a country by assessing the monetary value of all finished goods and services produced within a country's borders during a specific time period, typically a year. This metric encompasses consumption, investment, government spending, and net exports, thus providing a comprehensive overview of an economy's activity.

In contrast, Net National Income (NNI) adjusts GDP by accounting for depreciation and income earned from abroad, making it a measure of national income rather than direct output. The Consumer Price Index (CPI) is focused on measuring inflation and changes in purchasing power from the consumer's perspective, rather than the total output of an economy. Lastly, the Balance of Trade reflects the difference between a country's exports and imports but does not measure overall economic activity or output directly. Therefore, GDP stands out as the most suitable metric for measuring national output.