How the auction simulator re-clears your own orders
Enter the ladder your firm submitted into an auction and re-clear the published aggregate without it, or with a different one in its place. It answers what your orders were worth to the clearing price, which is a different and more useful question than what share of the volume they were.
Nothing you type leaves the browser
The ladder you enter is held in the browser tab only. It is not sent to a server, not written to the URL and not stored, which is also why it does not survive a reload and why this page cannot be shared by link in the state you are reading it.
That is a deliberate constraint on the product rather than an implementation detail. A submitted order ladder is among the most sensitive things a desk holds, and the only way to promise it is not retained is not to receive it. The re-clear therefore runs in the browser, against the same engine the screens use.
What the re-clear actually does
- 1. Take the published aggregate
- The aggregated supply and demand curves for that area, auction and delivery period, as published.
- 2. Remove your ladder from it
- Your steps are subtracted from the side they were submitted on, leaving the book as it would have been without you.
- 3. Re-cross the curves
- The crossing of the remaining book is the counterfactual clearing price.
- 4. Report the difference
- Cleared price minus counterfactual price. That difference is what your orders moved the auction by.
Entering a different ladder rather than none answers the adjacent question: what the auction would have cleared at had you submitted something else.
What the counterfactual assumes
One assumption, and it is load-bearing: that everything else would have been submitted unchanged. In a real auction other participants observe and respond, so the true counterfactual is unknowable and this is the conservative stand-in for it.
It inherits every limit of the aggregated curve underneath it. Block orders cannot be represented. Where the published book covers a whole coupled group rather than one zone, the re-clear covers that group. And a delivery period with no published curve cannot be simulated at all - the page says so rather than offering an empty ladder to fill in.
What it is for
Chiefly disclosure sizing and post-trade review. A large share of the volume that moved the price by nothing, and a small share that moved it materially, are different facts, and share alone cannot separate them.
It produces no finding and no determination. It is arithmetic over a published aggregate, run at your request on numbers you supplied.