President Biden has proposed a new "billionaire tax" on Americans worth over $100 million as part of his 2025 budget. A wealth tax is a broad-based tax on the total value of assets owned by wealthy individuals, unlike income or capital gains tax. Experts say targeted wealth taxes starting at a high threshold can be most effective at generating revenue from the very wealthy. Critics argue wealth taxes risk capital flight as the mobile super-rich move assets to tax havens. Data shows wealth taxes raise a small portion of revenues where applied, and revenues don't always increase over time.