Spreading $12,000 over a year feels safer. Investing it all at once won 63% of months since 1871.

Every month since 1871 as a possible start day: lump sum or a 3 to 36 month drip into the S&P 500? Scrub 1,869 months of real data, set the interest on waiting cash, and find the rate at which the drip wins half the time. History, not advice.