The Forbes 400 is an annual list published by Forbes magazine that ranks the 400 wealthiest individuals in the United States. The list includes billionaires from various industries, such as technology, finance, and entertainment, and is based on their estimated net worth. The rankings are determined by assessing the value of assets, investments, and other financial holdings. The Forbes 400 serves as a snapshot of wealth in America, highlighting trends in wealth accumulation and the impact of economic changes on the richest individuals.