Ask a perp venue for a market’s open interest and you get one number: the contracts open at this moment. Ask what it was yesterday and, for the stock perps, there is nothing to ask. The venue serves price history and funding history. It does not serve open-interest history.
Why the level is not enough
Open interest of $349 million means little alone. It is large or small only against what it was. Up a fifth in a day while price climbs says new money is arriving on the long side. Up a fifth while price falls says the new money is short. Flat while price moves says the move is existing positions changing hands. The level is the same in all three and the readings are opposite.
That is the same price-against-open-interest logic the crypto map uses for coins, described in the price and open interest quadrant. It needs two points in time. A venue that hands you one gives you half a measurement.
History cannot be bought afterwards
Some data can be backfilled. Prices can, because candles are archived. Open interest that nobody recorded is gone. You cannot reconstruct last Tuesday’s figure from anything published today.
So the only way to have it is to have been writing it down. NoVo’s collector started recording every stock and index perp on 4 October 2026: open interest, funding and premium, every pass. From that day forward there is a history. Before it there is none, for us or for anyone who was not doing the same.
Honest labels while the record is young
A young record creates a temptation to call a thirteen-hour average a weekly one. The dashboards do not. The column heading states the span the record really covers, in hours, and switches to seven days when there are seven days behind it. An open-interest change is measured against the reading nearest 24 hours back, and when the record is younger than that, against the oldest reading there is, with the true span shown.
A missing hour stays missing. If the collector was down, the chart shows a gap. Carrying the last value forward would draw a flat line over a period nobody measured.
What it becomes
In a month the record answers questions nothing else can: whether open interest on a name builds into earnings, what funding does over a weekend, how the S&P 500 perp behaves ahead of a cash open. Each of those needs months of hourly rows. The rows are being written now so the answers exist later.