Dollar-cost averaging vs lump sum: I ran the actual numbers over 20 years of historical data and here's what I found.

Lump sum investing (putting all available cash to work immediately) outperforms dollar-cost averaging about 66% of the time historically, because markets go up more often than they go down over medium and long time horizons.

But here's what the studies don't emphasize: the difference in outcomes is usually small — often 1-2% in final portfolio value. And the behavioral cost of lump sum investing is significant for many people. Investing a large sum and watching it drop 15% in the first three months causes panic selling far more often than a gradual entry.

My conclusion: lump sum wins on expected value. Dollar-cost averaging wins on the behavioral margin for most people. If you know you'll hold through a short-term drop, lump sum. If you're not sure, DCA is the insurance policy worth paying for with slightly lower expected returns.