Also called uptick, downtick
Tick rule
A way to guess which side started a trade: a print above the previous one is called a buy, below it a sell, equal keeps the last call. A proxy, since the feed does not say who crossed.
Updated 2026-09-16
A trade has two sides and a feed rarely says which one crossed the spread. The tick rule is the old proxy: if a print is higher than the previous print, call it a buy; lower, call it a sell; the same price keeps the previous call. It is what the desk's green and red on the tape mean.
It is right often enough to be useful and wrong often enough to matter. A buyer lifting the ask after a downtick reads as a sell until the next print. Academic work puts it around 75 to 85 percent accurate on liquid stocks; on thin names with wide spreads, less. Treat a single print's colour as a guess and a run of the same colour as information.
See also
- Time and sales — The running list of executed trades: time, price, size. Reading it is watching who is actually paying up, as opposed to the book, which is what people say they would do.
- Bid-ask spread — The gap between the highest price a buyer will pay and the lowest a seller will accept. It is the cost of trading, and you pay half of it on the way in and half on the way out.
Educational content, not investment advice. Angie explains how a valuation is built so you can judge it yourself. What you do with that is your call.
