Odds-On Imperfection: Monte Carlo Simulation

Financial-Planning Tool Fails to Gauge Extreme Events

If one had asked a financial adviser 18 months ago for retirement-planning guidance, there is a good chance he would have run a "Monte Carlo" simulation. This calculation method, as it is commonly used in financial planning, estimates the odds of reaching retirement financial goals.

But there is little chance your Monte Carlo simulation, named for the gambling mecca, would have highlighted a scenario like the market slide just seen. Though these tools typically run a portfolio through hundreds or thousands of potential market scenarios, they often assign minuscule odds to extreme market events. Yet these extreme events seem to be happening more often...

WSJ: Odds-On Imperfection: Monte Carlo Simulation