The Birthday of Andrew Carnegie (1835) – Mathematics of Philanthropy

Carnegie made a fortune in steel then gave it away. The mathematics of philanthropy: endowment sustainability (withdrawal rate, interest rates), grant optimisation (maximising social impact per dollar), and risk analysis (probability of ruin). The ‘Carnegie Rule’ says that endowment spending should be limited to the real return (≈5%). His foundations use mean‑variance optimisation for investment. Giving money effectively is a mathematical problem – one that Carnegie tried to solve. Steel and numbers built libraries worldwide.