Week 1, 2026

A trading day's board is the 1000 largest US-listed companies by market cap at its close: each company at its last trade on IEX in the regular session, times the latest share count it reported to the SEC on or before the day; ranks are positions on that board. An issue compares the close of its week's last trading day, usually a Friday, with the close of the week before's, and is rewritten only when a fix to the ranking rules rewrites the days it reads. Every sentence on the page is written from the numbers by a fixed rule; nothing is edited by hand. Every past day was ranked from that day's own prices and counts; details on the about page.

A reading is placed in the year of trading, 252 trading days, ending on the issue's close. "Higher than on 92% of days this year" counts the trading days in that year with a lower value, and "the most since" names the last day before the week when the reading was at least this high, or this low for a falling one; it is left out when that day is within a fortnight. Weeks are numbered as ISO weeks, Monday to Sunday. For runs and places the year's weeks run close to close: a run counts consecutive weeks moving the same way, and a week's place ranks its move against the year's other weeks in that direction.

IEX doesn't trade every company every day, and a company it didn't trade isn't ranked that day, so each end of the week is the top 1000 by market cap among the companies on that day's board plus any the board missed in the four trading days before while its last market cap was at least twice the smallest on the board, each at its latest market cap and price; a rank is a position in that list. A missed day never reads as a departure, and a company that slipped past the cutoff leaves at once. The companies that entered are the ones in the end list and not the start list, and the companies that left the other way round, so the two counts are equal. Who moved it is each company's market cap at the end of the week less its market cap at the start, a company that entered counted in full and one that left counted out in full; the risers' sum and the fallers' sum are reported as they are, and their difference is close to but not exactly the total's move. A company's market cap also moves when it reports a new share count.

Price changes are taken over the companies ranked at both ends of the week, a price before an official split divided by its ratio; the middle company is the median, half the companies above it and half below. A hundred with fewer than ten such companies does not compete for best or worst, and the bottom hundred is biased upward, because the companies that fell out of the top 1000 during the week are not in it. The top 1000 as one index is the board's own: each trading day, the change of every company on the board the day before, weighted by its market cap, so companies coming and going and share counts changing do not move it. Industries are the ones the SEC files companies under, the names of their SIC codes, with at least 15 companies.

Breadth is the share of the board priced higher than 30 trading days earlier, over the companies that had a price then. Market correlation is the mean correlation of daily changes, pair by pair, among the 50 largest companies at the issue's close, over the last 30 trading days; dispersion is the spread of a trading day's changes across the 100 largest, averaged over the last 30 trading days; the top 10's share is the 10 largest companies' market cap as a share of the top 1000's. The today page draws each of the four over the year and reads it on the latest trading day. The volume is IEX's own, a slice of the whole market's, so nothing here is read from it.

The fourteen indicators are computed as on the stock indicators page, from the trading days alone, and are defined on the about page. At each close the middle company is taken among the top 200 over the companies with a value that day, leaving out only a company that moved less than 0.25% a day over the last 30 trading days; a day with fewer than 20 such companies has no value. The zone shares are over the same companies at each close, and the shift the reading names is the zone whose share moved the most between the two, on any of the fourteen.

Three readings look back over every close-to-close week the dataset holds up to this issue. The fifty biggest climbers and fallers of a week are followed into the week after: the price change of the middle company among them, and of the middle company of the whole board, each the middle value over those weeks ("typically"), with the count of weeks in which the group did better than the board. The number in brackets after a move in the movers lists is the middle value, over the same weeks, of how many places a company that started the week in the same hundred of the board moved, up or down. The industry readings count, over consecutive weeks with at least eight industries in common, how often the first industry stayed first, and how many of a week's five best industries were among the five best the week after.