Net Domestic Product (NDP) is a measure of a country's national income and economic activity. It is calculated by subtracting the value of depreciation from the Gross Domestic Product (GDP). Depreciation refers to the wear and tear that occurs on the country's fixed assets, such as buildings, machinery, and infrastructure over time.

NDP is an important measure because it takes into account the loss of value due to the wear and tear of the country's assets. This allows for a more accurate representation of a country's economic growth and development.

NDP is also used in analyzing and comparing the economic performance of different countries. It provides insight into the effectiveness of policies and investments on economic growth. Additionally, it is used by businesses and investors to assess the economic health of a country and make informed decisions about investing or expanding operations.

In summary, NDP is a measure of a country's national income that accounts for the depreciation of fixed assets. It is used in analyzing economic growth and development, comparing countries, and making investment decisions.