Perpetuals often trade more volume than the spot market for the same coin. Leverage, no expiry and a single deep book make the perpetual the venue of choice for active traders, while spot is where holders transact.
That inverts the equity relationship, and the consequences run through everything.
Price discovery moves
When the derivative is deeper, it is frequently where price is discovered, and spot follows — the reverse of the usual assumption in where the price is actually made. Reading a spot chart as the market and the perp as a shadow of it gets the causation backwards for many coins.
The index is built on the thinner market
This is the awkward one. The index that sets funding and the mark is computed from spot venues — deliberately, since spot is harder to manipulate through leverage.
So the deep market is anchored to the thin one. In calm conditions that is fine. In a violent move it means the reference governing every margin calculation is coming from books with less depth than the market being referenced.
What it changes for sizing
Size against the book you will exit into. If your position is on the perpetual, perp depth is the relevant constraint — and it is usually better than spot depth, which is one of the few places crypto microstructure works in a trader’s favour.
But an exit that requires converting to spot faces the thinner market, which is the hidden leg in cash-and-carry and in any strategy that ends in the underlying.
The read
Compare the two rather than assuming a hierarchy. Their relative depth differs by coin, and it tells you which market is setting the price and which is along for the ride.