Source of wealth describes the primary way a billionaire accumulated their fortune. Common sources include: founding a technology company (Elon Musk — Tesla, SpaceX), inheriting a family business (the Walton family — Walmart), building a fashion/luxury empire (Bernard Arnault — LVMH), real estate development, finance (hedge funds or investment banking), or energy (oil, gas, or renewables).
Forbes and Bloomberg both track source of wealth as part of their billionaire profiles. Self-made billionaires — those who built their fortune from scratch — are generally distinguished from those who inherited wealth. Studies suggest approximately 70% of Forbes billionaires are considered "self-made."
Understanding source of wealth is important for assessing the sustainability and concentration risk of a billionaire's net worth.