How Many ETFs Do You Need? Belgian Guide

📅 Last updated: 8 May 2026
 ·  🏷 Topic: ETF, portfolio, diversification
 ·  🇧🇪 For: Belgian investors

A frequently asked question from Belgian beginners: how many ETFs should I buy? 5? 10? 20? The answer is almost always: fewer than you think.

The short version

For most long-term portfolios, one to three ETFs are enough. More ETFs does not give more diversification — often only more overlap.

Three worked examples

1 ETF (simplest):

• VWCE or FWIA (FTSE All-World) — global equities, developed + emerging markets in a single fund.
• ~3,700 underlying positions.
• No rebalancing needed.
• One click per monthly purchase.

For anyone who wants absolute simplicity: this is enough. No shame in it.

2 ETFs:

• IWDA (88%) + EIMI (12%) — developed markets + emerging markets separately.
• Advantage: lower TOB on IWDA (0.12% vs 1.32% on VWCE).
• Disadvantage: you need to rebalance between the two once a year.

3 ETFs (advanced):

• IWDA (75%) + EIMI (12%) + small-cap ETF (13%).
• Adds a small-cap tilt — smaller companies that historically deliver slightly better returns over the long term.
• More work, marginal added value for most retail investors.

What you do NOT want

Mistake: 5 funds that do the same thing.

A common beginner mistake is a portfolio of:

• VWCE (world)
• IUSA (S&P 500)
• ESI0 (Eurostoxx)
• BEL 20 tracker
• Nasdaq 100

Sounds diversified. It isn’t. VWCE already contains ~62% US, ~13% European. Adding an S&P 500 doubles your US exposure. Adding a Nasdaq doubles your US tech exposure. Adding a Eurostoxx doubles your Europe exposure. Result: more concentration, not less.

What the math says

Studies show that ~30 randomly selected stocks are enough to diversify away most company-specific risk — what remains is systemic risk (the market itself), which you cannot diversify away by adding more names.

A world-index ETF has 1,300–3,700 positions — well above that diversification threshold. A second world ETF adds barely anything if the two track the same index.

What CAN justify extra ETFs

• Asset-class diversification — an equity ETF + a bond ETF + a real-estate ETF represent different sources of risk. That is real diversification.
• Geographic tilt — for example, extra emerging markets if you expect them to grow structurally faster.
• Factor tilt — value, quality, small-cap as added “flavour” on top of a world base.

Practical recommendation

Start with one world-index ETF. Add a bond ETF when you want a more defensive profile (typically 30+, or as your horizon shortens). Add a real-estate ETF (GVV) or an EM ETF only if you have a specific reason — not “for the diversification”.

💡 Simplicity scales. One ETF in your portfolio is not amateurism. It is often the most robust choice for anyone who wants to stay disciplined for 30 years.

Sources

1. Wikifin — Diversification and ETFs
2. SPIVA Europe — Active vs passive study
3. Curvo — Best ETF for Belgium 2026