Gross national income (GNI) is a metric used by economies to measure their collective wealth. GNI differs from gross domestic product (GDP), estimating key factors of a nation's economic output, such as the income it receives from abroad. GNI reflects not only the production and consumption of goods and services within a country (as GDP does) but also foreign investment, the value of resources extracted by foreign companies, and the transfer of capital across borders.

GNI is a measure of the economic output or total national income of a nation's citizens combined with income earned by its citizens abroad. It is calculated by adding all the money a country earns from foreign sources and subtracting the amount of money it pays to other countries. As such, GNI provides a broader measure of a country's economic health than GDP, which only measures the value of goods and services produced within a nation's borders.

GNI is useful for comparing the economic performance of different countries. It gives a measure of the true size of a country's economy that takes into account both domestic and international investment. It gives a truer picture of economic performance because it incorporates the effects of global trade, and reflects the balance of payments of a country.

GNI is also useful in assessing the economic stability of a country by looking at trends over a longer period of time. This, combined with other data, allows economists to make informed decisions about economic policy.

In conclusion, gross national income (GNI) provides a more comprehensive overview of a nation's economic health than gross domestic product (GDP). GNI measures the collective wealth of a nation's citizens and includes foreign investment, the transfer of capital across borders, and the value of resources extracted by foreign companies. In this way, GNI provides a truer picture of a country's economic performance and factors into informed economic policy decisions.