Week 6 Day 6: Small and Consistent Beats Large and Sporadic

$200/month for 20 years at 7% becomes roughly $104,000. $5,000 every 2 years for 20 years (same $48,000 total contribution) becomes roughly $88,000 at 7%. The monthly investor wins by $16,000 because their money entered the market earlier and more consistently. Time in the market beats timing the market.

The monthly investor benefits from dollar-cost averaging and continuous compounding. Every monthly contribution starts compounding immediately. The lump-sum investor's money sits in a savings account for up to 23 months between investments, earning little to nothing. Over 20 years, those idle months add up to years of lost compounding. But there is a subtler advantage: the monthly investor never needs to make a 'big decision.' Writing a $5,000 check feels like a major financial event. It triggers deliberation, second-guessing, and sometimes paralysis ('Is now the right time?'). A $200 automatic transfer is invisible. No decision fatigue. No timing anxiety. The mechanical regularity of small contributions eliminates the behavioral obstacles that cause lump-sum investors to delay, skip, or abandon their plans.

Vanguard's research on lump-sum versus dollar-cost averaging shows that lump-sum investing beats DCA roughly 68% of the time when you have the money available. But this analysis assumes you actually invest the lump sum immediately. In practice, behavioral friction often delays lump-sum investments by months or years, eroding the theoretical advantage. A 2019 study by Morningstar found that investors who intend to make annual lump-sum contributions actually follow through less than 60% of the time, with the average investor missing 1-2 planned contributions over a 10-year period. Automated monthly investors, by contrast, have follow-through rates above 90%. The mathematically optimal strategy that you execute 60% of the time loses to the slightly suboptimal strategy that you execute 95% of the time. Behavioral consistency is the dominant variable.