Synthetic ETF — How does it differ from physical ETF?
What is a synthetic ETF? How synthetic vs physical replication works, what are the risks, and when is it worth choosing a synthetic ETF?
What is a synthetic ETF?
A synthetic ETF is an index fund that doesn't directly buy stocks or bonds that make up the index. Instead, it uses swap contracts with an investment bank (counterparty) to replicate the index performance.
How does physical replication work?
A physical ETF buys all (or most) securities from the index. If you're tracking the S&P 500, the fund buys 500 stocks in appropriate proportions.
Advantages: Simplicity, no counterparty risk. Disadvantages: Higher transaction costs (especially for large indices), tracking error from rebalancing costs.
How does synthetic replication work?
A synthetic ETF holds a collateral basket — often other stocks or bonds — and enters a swap contract with a bank. The bank commits to pay the fund the exact index return in exchange for the return from the collateral basket.
ETF ← swap → Investment bank
ETF provides: return from collateral basket
Bank provides: return from target index
Counterparty risk
The main concern with synthetic ETFs: What if the counterparty bank goes bankrupt? In practice:
- UCITS regulations limit swap exposure to 10% of fund assets.
- Most synthetic ETFs use overcollateralization — collateral exceeds 100% of value.
- Large banks (Goldman Sachs, Deutsche Bank) rarely go bankrupt, but the risk exists.
When is a synthetic ETF better?
- Hard-to-access markets — E.g., Chinese indices (CSI 300), where direct stock purchases are restricted.
- Lower tracking error — Swap guarantees exact index return.
- Tax efficiency — In some jurisdictions, synthetic ETFs avoid withholding tax on dividends.
Examples
| ETF | Replication | Index |
|---|---|---|
| iShares Core MSCI World (IWDA) | Physical | MSCI World |
| Xtrackers S&P 500 Swap (XDPD) | Synthetic | S&P 500 |
| Lyxor MSCI EM (LEMC) | Synthetic | MSCI Emerging Markets |
Which to choose?
For most retail investors, a physical ETF is the safer and simpler choice. Consider a synthetic ETF when you want access to an exotic market or minimal tracking error is crucial.
How Freenance can help?
Freenance tracks both types of ETFs in your portfolio. You see composition, costs, and performance regardless of replication method — all in one dashboard.
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