RE: Closing Auction20 Jun 2026 08:07
“To fulfill their legal mandate to mirror the index”
Just to be clear that there is no “legal mandate” (that looks like an AI hallucination).
The fund has an *objective* to track *the returns of the index*, not an absolute requirement *to replicate the index*. They seek to minimise tracking error, not eliminate it.
So a fund can choose when and whether to hold a share - either for a period or at all. Not all funds even choose to replicate an index, with some sampling it.
If you think about, a share entering the index is just 1 in 250 (0.4%) of the index.
And it’s actually not even that for SSIT as the index is mar cap and free float weighted.
If you do the maths then that puts SSIT at around 0.15% of the FTSE 250 index. It’s 0.015% of the FTSE350. Both of which are acceptable tracking errors.
At the bottom of the FTSE250 it’s relatively common for a share to be promoted into the index and relegated quickly - so some funds hold off buying until the share has been in the index for 6 months or so.
So, there is absolutely no rush for the funds to buy SSIT
The fund managers aren’t stupid and have done this before - so they know that them all piling into the share create a temporary, artificial peak that will result - itself - in a tracking error.
It’s the same with the shares that are exiting. There is no rush to sell. Not for the FTSE250/350.
An “interesting” side note…
You’d have thought that SpaceX’s $2.4tn mar cap - around 6.5% of the NASDAQ 100 - would mean that it’s a *must buy*. But the maths are subtler as the NASDAQ 100 is free float adjusted and SpaceX has an unusually low free float at the moment of 4%. Adjusted that makes SpaceX currently just 0.5% of the NASDAQ 100, which is what QQQ tracks - so there is a bit less pressure for funds to pile in than you’d expect. It’s not the case that they can choose to not hold it, but they have the ability to feather in their buying.
Hope that all helps.