Never pause DCA during downturns — they are when it works best

Buying more shares at lower prices is the mathematical mechanism behind DCA — pausing during dips captures only the losses.

Why it works

DCA’s sole mathematical advantage over lump-sum investing occurs specifically when prices fall during the accumulation period — you buy more shares at lower prices, reducing average cost per share below the time-weighted average. The investor who pauses DCA during a downturn — the most common behavioral failure — captures all the price drops as unrealized losses while buying fewer shares at the prices that drive eventual recovery.

How to do it

1. Write down the commitment before the next market drop: "I will continue the automatic transfer regardless of portfolio value."
2. When a downturn hits, check the share count, not the portfolio value — more shares is the right frame.
3. If the urge to pause is strong, reduce the amount by no more than 25%, but do not stop entirely.

Evidence

DCA’s mathematical property of lowering average cost basis is demonstrable from first principles; behavioral research on investor underperformance confirms that timing decisions — including pausing contributions — are a primary driver of the gap between fund returns and investor returns. (mechanistic)

DALBAR’s methodology has been criticized for overstating the behavior gap; the direction of the effect (timing decisions hurt returns) is broadly accepted even where the magnitude is disputed.

Sources

• DALBAR Annual Quantitative Analysis of Investor Behavior (ongoing) — documents the persistent gap between market and investor returns driven by timing behavior

Common mistake

Telling yourself "I’ll resume when things stabilize," which guarantees you miss the early recovery shares that drive the compounding advantage of buying low.