Four kinds of answer to 'which market'
Index providers publish families of indices, and the family tells you what question the index was built to answer. Four of them cover most of what you will meet.
A broad market index is a slice of the whole listed universe by size — the largest fifty, the largest hundred, the largest five hundred. A sectoral index takes one part of the classification from 01.05.02 and holds only that.
A thematic index gathers companies connected by an idea that crosses sectors, such as consumption or energy transition. A strategy index applies a rule about a characteristic — low volatility, quality, equal weighting — rather than taking size as it comes.
Four families, four questions
Tap each. The right benchmark is the one built to answer your question.
A strategy index is the one most often mistaken for skill. Nobody is choosing; a rule is being applied, on a schedule, exactly as in 01.05.04.
How the wrong yardstick misleads
Suppose a portfolio holds only small companies and it is compared with a large-cap benchmark. In a year when small companies do well the portfolio looks brilliant, and in a year when they do badly it looks incompetent — and in neither case has the comparison told you anything about the person managing it.
The comparison only carries information when the benchmark represents the choices that were genuinely available. That is what makes it a control rather than a decoration.
This is also why a fund states its benchmark rather than leaving it open. The stated benchmark is the standard it has agreed to be measured against, and you are entitled to check that the standard fits what the fund actually holds.
A fund holds only banking companies and reports that it beat a broad fifty-company index this year. What have you learned?
What you can take from all this
You now have the map of the universe. Companies are ranked by size into categories that are republished twice a year. They are classified by what they earn from, at four levels. Indices take slices of that, weighted by the part of each company that is actually available. Those lists are reviewed on a calendar, and money follows.
The single most useful habit from this chapter is small: when someone compares a result to 'the market', ask which index and check that it fits. Most claims that sound impressive stop sounding impressive at that point.
None of this tells you what to buy, and it is not meant to. It tells you how the universe is organised, so that later chapters have somewhere to stand.
Companies mapped, sorted and indexed. The next chapter looks at what happens when someone packages a slice of that map and sells it to you as a single unit.