📅 Last updated: 8 May 2026
· 🏷 Topic: DCA, lump-sum, market timing
· 🇧🇪 For: Belgian investors
Dollar-cost averaging (DCA) is the principle of investing a fixed amount at fixed intervals — e.g. €200 every month — rather than investing a large amount all at once (“lump-sum”). Which strategy wins historically?
The mathematical conclusion
Research (including Vanguard’s classic 2012 study and repeated analyses since) shows that lump-sum investing historically outperforms DCA ~66% of the time, with on average ~2-3% higher returns.
Reason: markets go up over the long run. Money that is in the market earlier benefits from returns for longer.
But…
Lump-sum requires psychological resilience. Suppose you inherit €30,000 and put it into a world ETF today. Three months later, the market drops 20% — your portfolio is €24,000. Anyone who panic-sells at that point locks in the loss.
DCA reduces this risk: by buying gradually, you buy more cheaply in a falling market. Psychologically, it’s much easier to keep going during a dip.
So when is DCA more advantageous?
- When you are sensitive to losses. Anyone who can’t emotionally handle a 30% drawdown is better off with DCA.
- When you don’t have a lump sum. For someone who simply saves €200-500 each month, “DCA” isn’t even a choice — it’s just how it works.
- In overvalued markets. If the market is at all-time highs and you’ve just received €50,000 from an inheritance, lump-sum often feels risky. DCA can then be the better psychological choice — even though it’s mathematically suboptimal.
The practical compromise
For lump-sum amounts >€10,000: spread over 3-6 months. Not 5 years — that’s excessively slow. 3-6 months gives you psychological comfort without giving up much return.
For monthly contributions: automate and stop overthinking. €200/month into VWCE or IWDA, done. This is DCA in action and it’s the right route for most Belgians.
Belgian TOB impact
In Belgium, DCA has a downside that doesn’t exist in the US/UK: TOB (stock-exchange tax) on every purchase. Anyone who buys a Belgian-registered accumulating ETF (e.g. VWCE) every month pays 1.32% TOB on each purchase. Example: €200/month = 12 × €2.64 = €31.68 TOB per year (1.32% of total invested).
Practical optimisation:
- For low monthly amounts (<€500): buy quarterly or half-yearly to reduce TOB overhead.
- Or choose an ETF with low TOB (IWDA = 0.12%) instead of VWCE (1.32%).
See IWDA vs VWCE(NL) for the detail.
Common mistake
Waiting for the “right price”. Anyone who says “I’ll wait until the market is 10% lower” before getting in — that moment often doesn’t come, and when it does, the psychological barrier to buying is often even greater.
Research (Schwab, Fidelity studies) shows that almost no one can consistently time the market. The best time to start was 10 years ago. The second best time is today.
🔗 For the psychological side of investing: see Behavioural finance(NL).
2026 Belgian capital gains tax
Since 1 January 2026, Belgium applies a 10% capital gains tax on realised gains from shares, ETFs, bonds and crypto. The first €10,000 of net gains per year is exempt, so most retail DCA portfolios fall well under the threshold. The tax does not change the lump-sum vs DCA arithmetic — it applies on sale, not on purchase.
Sources
- Vanguard — Lump-sum vs DCA studies (2012, repeated analyses)
- SPIVA Europe — Market return studies
- Schwab — Market timing research
Transaction costs: where monthly investing goes wrong in Belgium
The real objection to monthly investing in Belgium is not the maths but the per-order cost. Twelve trades at €5 with Bolero is €60 a year, against €5 for a single purchase. On a €200 monthly contribution that is 2.5% of the amount invested — more than the TOB.
Two ways to remove that cost
- DEGIRO Core Selection — the first trade per ETF per calendar month is commission-free regardless of size (only a €1 handling fee). A second trade in the same ETF that month is charged normally.
- MeDirect — commission-free ETFs on a monthly investment plan.
- Quarterly purchases at Bolero or Keytrade — if you stay with your broker, four orders a year instead of twelve keeps costs proportionate at almost no loss of spreading.
What about a lump sum (inheritance, bonus, savings)?
- Mathematical optimum: invest everything immediately.
- Psychological optimum: spread over 3-6 months — not years, which is excessively slow.
- Hybrid: half immediately, the rest spread.
The two costliest mistakes
- Never raising the amount. Inflation and wage growth make €200 in 2030 worth less than €200 today.
- Stopping during a crash. Crashes are precisely when prices are best; panic-stopping locks in the loss.
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