01 The mechanism
Think in units, and red months change colour
The mental shift that makes DCA click: you aren't buying "the market", you're buying units of it. Same $300 every month, through a rough patch:
| Month | Unit price | Your $300 buys |
|---|---|---|
| January — all calm | $10 | 30 units |
| March — scary headlines, −40% | $6 | 50 units |
| June — recovering | $8 | 37.5 units |
| Result | avg price paid: $7.66 | 117.5 units for $900 |
The average price across those months was $8 — but you paid $7.66, because your fixed dollars automatically bought more units when they were cheap. Nobody timed anything; the arithmetic did the buying-low for you.
For your money: for anyone still contributing monthly, a falling market is — strange but true — a sale on the units your future self will live on. The worst decade to feel was often the best decade to have been quietly buying through.
For your life: this is the maths that turns red headlines from threat into noise. You don't have to feel brave in March; the standing order is brave for you. That's the whole design.
02 Full candour
The honest debate: lump sum usually wins
Here's what a less candid page would skip. If you're holding a windfall — an inheritance, a bonus, a severance — and drip it in slowly, Vanguard's research across three countries found that investing it all at once beat the slow drip about 68% of the time. Markets rise more often than they fall, so cash waiting in line usually just misses growth.
No — the study is about lump sums. Most people don't have one. They have a salary, arriving monthly. Investing it as it arrives isn't a strategy choice — it's the only option, and it happens to carry DCA's discipline built in.
The maths says invest it; the psychology says a −30% month after doing so breaks people. A sensible compromise we often use: a defined schedule — in over 6–12 months, fixed dates, no discretion — trading a little expected return for a lot of survivability.
03 The real product
What DCA actually manufactures: behaviour
Strip the maths away and DCA's true output is this: it removes every monthly decision — and decisions are where returns go to die. The behaviour gap (investors earning ~1.1 points a year less than their own funds) is made of exactly the choices a standing order never gets to make: waiting for clarity, pausing "until things settle", doubling in after a good year.
- No decision each month means no timing mistakes each month — a mistake rate of zero, by construction.
- The habit survives busy seasons, newborns and news cycles — the plan runs whether or not you're watching.
- It scales with life: the right response to a raise is often just a bigger drip, banked before lifestyle meets it.
04 Making it real
In practice: the three settings that matter
| Setting | The guidance |
|---|---|
| The date | Payday, or the day after — pay the future first, spend what's left; never the reverse |
| The amount | Set by your plan (your savings rate), not by mood — and revisited at raises, not at headlines |
| The rule | It runs in red months. Especially in red months — that's when the units are on sale. If the urge to pause it ever wins, read this first, then call me |
Drip beats guess — not because the maths always favours it, but because the person who drips never has to be right about anything. Set the standing order, size it to the plan, and let a decade of Tuesdays do what no forecast can. Keeping the drip flowing — and sized to your seasons — is part of what I watch so you don't have to.
Sources & notes
Figures updated 2026. Lump sum vs cost averaging (~68% of historical periods favoured immediate investment; US/UK/Australia, MSCI World, 1976–2022): Vanguard, "Cost averaging: Invest now or temporarily hold your cash?" (2023) — their finding concerns windfalls, not salary investing. Behaviour gap (~1.1pp/yr, decade to 2023): Morningstar Mind the Gap. The unit-maths table is our own illustration — the arithmetic is definitional, not empirical. Nothing here is a forecast of any market's path.
General information, not financial advice. Jonathan Wong is a licensed financial adviser representative in Singapore, currently between firms — during that period he is not able to provide financial advice. You can check his registration yourself on the MAS Financial Institution Representatives Register at eservices.mas.gov.sg/rr.