ETF v praxi
Why ETF Size and Age Matter: AUM and Inception Date
Key takeaways
- AUM (assets under management) is the total assets of the fund — the higher it is, the lower the operating costs and the tighter the spread.
- A small fund (under EUR 100 million) can be closed or merged even if it would otherwise be a good choice.
- The inception date shows how long the fund has actually been operating — a short history does not guarantee that the data are meaningful.
- An older fund with a longer track record better illustrates behavior under various market conditions including crises.
- AUM and age are supplementary filters — not a substitute for analyzing TER, tracking error, and index composition.
When selecting an ETF, most investors look at return and cost (TER). AUM — the fund's total assets — and the inception date are equally important filters that guard against less obvious risks.
What AUM is and why it matters
AUM (Assets Under Management) is the total value of assets managed by the fund. For large funds (billions of euros):
- A narrower spread between the buy and sell price — the fund is liquid and market makers maintain a tight spread
- Lower real operating costs per investor — fixed costs are spread across more units
- Stability of existence — a large fund is not worth closing even under adverse conditions
A small fund below EUR 100 million is functional but carries the risk of closure — being shut down or merged with another fund. That does not mean a loss, but it does mean a forced sale (and potentially a taxable event) at an inconvenient time.
What the inception date reveals
The fund's inception date affects the available data. A fund launched in 2020 has never experienced a bear market like 2008–2009 or the February 2020 crash. Its historical performance is shorter and less informative.
An older fund — for example with a history going back to 2005 or 2010 — has gone through various market conditions. Its tracking error (deviation from the tracked index) and behavior during a crisis are better verified. This is relevant when comparing funds that track the same index.
AUM and age in practice: how to use them
The ETF selection process:
- Define the index you want to track (e.g. MSCI World, S&P 500)
- Filter ETFs with AUM above EUR 500 million and age above 3 years
- Compare TER and tracking error among the remaining candidates
- Check the domicile — for Czech investors ideally Ireland for tax efficiency on dividends (see why UCITS ETF Irish domicile)
An overview of additional selection criteria can be found on the ETF page.
FAQ
What is AUM in an ETF?
Assets Under Management — the total value of assets managed by the fund. The higher the AUM, the more liquid the fund, the tighter the spread, and the lower the risk of the fund being closed or merged.
How large an AUM is safe?
General guidance: at least EUR 200–500 million. Below this threshold the risk of closure (fund shutdown) increases. Large popular funds have AUM in the tens of billions — and their liquidity and stability reflect that.
Why does an ETF's inception date matter?
An older fund has gone through various market conditions — crises and growth alike. Its tracking error and historical performance are better verified. A new fund has a shorter history that may not reflect behavior under adverse conditions.
Can fund closure be disadvantageous for an investor?
Yes. Fund closure does not mean losing money, but it does mean a forced sale on a chosen date. If that happens at an inconvenient time (a downturn), you realize a loss. In the Czech Republic it may also trigger an unplanned taxable event.