Expense ratio
What it means
The annual fee a fund charges, shown as a percentage of your investment — for example, 0.03% means $3 a year on a $10,000 position.
Why it matters
Fees compound too, just against you. A fund charging 1% instead of 0.05% can cost tens of thousands of dollars over decades — checking this number takes thirty seconds and matters more than most people assume.
A worked example
Two funds, both returning 7% a year before costs, on a 100,000 balance held for twenty years. One charges 0.20%, the other 1.50%.
The cheap fund compounds at 6.8% and reaches roughly 373,000. The expensive one compounds at 5.5% and reaches roughly 292,000. The difference is about 81,000 — the fee was 1.3 percentage points a year, and it consumed close to a fifth of the final balance without either fund doing anything differently.
What people get wrong
"Only 1%" is the error, and it comes from reading the fee as a percentage of returns rather than of the balance. It is charged on everything you hold, every year, whether the fund gained or lost. In a year the fund falls 10%, you still pay it.
The other thing people miss is that the expense ratio is not necessarily the whole cost. Trading commissions, currency conversion, platform or custody charges and, in some markets, entry or exit fees sit outside it. The number worth comparing is total cost of ownership, which sometimes requires reading past the headline figure in the fund's own documents.
How this works in Latin America
Fee levels vary a great deal by market, and locally distributed funds in several Latin American countries have historically carried materially higher charges than large international index funds — a gap driven by distribution structures and scale rather than by anything the funds do differently with the money.
That makes the comparison worth doing explicitly rather than assuming. Set the total annual cost of a local product against an international equivalent available through your broker, then weigh the difference against the currency exposure and any tax consequences of holding abroad, which can run the other way. The point is not that one is always better — it is that a fee difference of a percentage point or more is large enough to be worth an afternoon of checking.