First, the key terms.

Holding
An underlying asset or position in a portfolio.
Weight
The fraction of portfolio value assigned to a holding.
Index
A rule-defined benchmark or collection of selected assets.

The idea, explained

A fund is a structure through which investors obtain exposure to underlying assets or a strategy. Its diversification depends on what it actually holds, not its number of units or its label. An index defines selection and weighting rules; concentrated sectors or a few large companies may dominate. Costs include fund expenses and potentially trading costs. Compare the holdings, objective and risks rather than assuming that every fund offers broad-market exposure.

STEP 1

Separate wrapper from strategy

ETF describes a fund that trades on an exchange. Index-following describes an investment strategy. An ETF can be actively managed, and an index strategy can be offered through another fund format. Start with the objective and holdings rather than the wrapper’s name.

STEP 2

Look through to the assets

Owning many units of one fund does not change its concentration. A fund with hundreds of holdings may still have large weights in a few companies or one sector. Owning several similar funds can duplicate exposures rather than diversify them.

STEP 3

Read costs and mechanics

Fund expenses, trading spreads, tracking differences and any special structure affect outcomes. An index is a benchmark; a real fund incurs implementation costs. None of these features makes future returns certain or eliminates market risk.

Follow a worked example.

Two funds each hold 100 securities. One spreads weight widely; the other places half its value in five companies. The same holding count produces very different concentration. Owning both may still duplicate many positions.

Walk it through, one step at a time

  1. Fund A allocates 50 percent to five companies and the remaining 50 percent across 95 companies.
  2. An investment of $1,000 puts $500 into the five largest positions collectively, despite the fund holding 100 names.
  3. Buying another fund with the same top five names may increase overlapping exposure. Compare weights across the combined portfolio.

Where people get stuck

An ETF can be concentrated, actively managed or leveraged; the wrapper is not a safety rating.

Now try it yourself.

Pause before opening each answer. Explain your reasoning in your own words.

1. Check the core idea

Is every ETF a passive index fund?

Reveal the answer & reasoning

No. ETFs can follow indexes or active strategies, and some use complex exposures. Read the fund’s objective and holdings.

2. Apply what you learned

If two funds both hold 100 stocks, must they have the same diversification?

Reveal the answer & reasoning

No. Their weights, industries, regions and overlapping holdings may differ. Count alone does not describe how risks are distributed.