What happens when a stock joins an index
Index funds are legally obliged to buy without regard to price. That is the only genuinely price-insensitive buyer in the market.
Understand a flow that has nothing to do with the business.
How What happens when a stock joins an index works, in one picture
The same argument as the text, as a chain. Each step is what makes the next one possible.
Who the first-day pop actually enriched
If the shares open 40% above the offer price, that 40% is money the company could have raised and did not. It went to whoever was allocated shares at the offer, which was not you.
- 1
Trackers do not have an opinion
A fund tracking an index must hold what the index holds. When a company is added, the fund must buy it, in size, near the effective date, at whatever price is available. Its view of the valuation is irrelevant, by design.
- 2
Which creates a predictable demand shock
The addition is announced before it takes effect. Everyone knows the buying is coming. So the price often rises between announcement and inclusion, as others front-run the forced buyers.
By the time the index funds actually buy, much of the move may already have happened, and prices frequently sag afterwards.
- 3
And the reverse is uglier
Deletion means forced selling, into a market that knows it is coming, in a company that is usually being removed because it has shrunk or deteriorated. Falling out of an index is a compounding indignity.
- 4
None of it is information about the business
The company is not better on the day it joins an index. The flows are mechanical. Confusing a flow with a fundamental is how people buy at the top of one.
You can distinguish a price move caused by flows from one caused by news.
Read next
Index funds are legally obliged to buy without regard to price. That is the only genuinely price-insensitive buyer in the market.
Every one shows its exact method, and the circumstances in which it is wrong. Free, and no account to look.