The biggest reactions on record

Why a page of single days

Every other page on this site reports a median, because a median is the honest way to describe what a release usually does. But nobody holds a position through the median. They hold it through a Tuesday, and the Tuesday is one of these. These are the twenty widest half hours on the record, each one a real date with a real report, ranked by high-to-low swing in the thirty minutes after the print. The last column is where the Nasdaq 100 closed that half hour, relative to the release price, so a large swing beside a small close is a round trip and a large swing beside a large close is a move that kept going.

What the list shows

The widest reaction on the record is CPI on 10 Apr 2024: 2.27% of travel in thirty minutes, closing the half hour at -1.66%. The jobs report holds more rows on the list than any other release, 7 of the twenty, and the two loudest releases on the ranking page account for most of it between them. What the list adds to the ranking is the shape of each release's worst days: two releases can sit side by side on the median and still differ in how far their widest half hours went, and that is what the biggest column on the ranking page is for. This page is the same information with the dates filled in.

Look for the rows where the swing is large and the close is near zero. Those are the days the market ran hard in one direction, reversed, and finished about where it started, and they are the reason this site measures swing rather than net change. A net figure calls a day like that a non-event. Anyone who held a position through it would not.

How I use the list

The median tells me what an ordinary release costs to hold through. This list tells me what an extraordinary one costs, and I size so that the second number does not end the account, not so that the first number is comfortable. It also tells me which releases produce the extraordinary days at all. There are jobs reports and CPI prints all over this list, a few FOMC afternoons, and almost nothing from the bottom half of the calendar. A release that has never made the list in three years is a release I am not going to lose sleep over.

What it cannot tell you

Twenty rows out of a few hundred releases is a list of tails, and tails are exactly the thing a small record measures worst. The list will change shape as the record grows; a day that is fifteenth now will be thirtieth in two years. The swing is the index, not the contract, and for the 08:30 releases it is the pre-market session, where the futures are the only thing trading and the index CFD tracks them at a small remove. And a wide day is not a prediction of the next one. The widest CPI on the list was followed, a month later, by a CPI that did not make it.