I'd Put Most of a Lump Sum Into an S&P 500 Fund Right Away. Here's When I Wouldn't.

Research shows that investing a lump sum into the S&P 500 all at once beats dollar-cost averaging about 70% of the time, even when buying near record highs. However, spreading purchases over 3 months may help risk-averse investors psychologically weather significant market downturns, though it typically results in lower returns.