Tick size is the minimum price increment a trading venue permits for quoting and execution.
Tick size is the minimum price increment a trading venue permits for quoting and execution. It is a market design parameter that constrains how finely participants can improve on the current best bid or offer. When a venue allows only larger price steps, traders have fewer admissible prices at which to post orders. When it allows smaller steps, traders can undercut or improve existing quotes by narrower amounts.
This mechanism directly affects the bid ask spread. Because the spread is measured in price increments, a coarser tick size can act as a floor under the quoted spread when the economically preferred spread would otherwise be smaller than one tick. A finer tick size relaxes that constraint and permits narrower quoted markets. In that sense, tick size does not merely coincide with spread width. It helps determine the set of feasible spreads a venue can display.
Tick size also shapes queue behavior through price time priority. If many traders want to provide liquidity at the same best price and the next admissible price improvement is relatively costly because the tick is large, more of that competition is forced into the time dimension. Participants then join existing queues and compete for execution priority by arriving earlier at the same price level. If the tick is smaller, improving the quote by one increment becomes less costly, so more competition can occur through price improvement rather than through joining an existing queue. That changes both queue length and the value of queue position.
Order placement strategies are therefore sensitive to tick size. With coarser ticks, passive traders face a sharper tradeoff between stepping ahead by one tick and preserving economics at the current quote. With finer ticks, small price improvements become a more practical way to gain priority, which can increase the frequency of quote revisions and one tick improvements. Conversely, where tick size is binding, traders may prefer to post at the best price and manage queue position rather than concede an entire tick to step ahead.
Across venues, cross venue data is the natural framework for studying these effects because the relevant outcomes are comparative. To assess how variations in tick size correlate with average spread width, queue priority, and price improving order frequency, the analysis would need venue level observations of quoted spreads, depth by price level, queue evolution under the venue matching rule, and the incidence of orders placed inside the prevailing spread.
The mechanism is clear from market structure: a venue with a smaller admissible increment lowers the cost of gaining price priority by a minimal amount, while a venue with a larger increment increases reliance on time priority at the same price.
For quantitative traders and microstructure researchers, the practical implication is conceptual rather than empirical in the present source set. Tick size is a binding discretization rule. It restricts the feasible spread, reallocates competition between price priority and time priority, and changes the incentives behind joining, improving, or canceling quotes. Any serious measurement of these effects should be done with cross venue order book and trade data, matched to venue specific tick regimes and analyzed at the level of spread states, queue states, and order placement events.
Covered in depth in the Cross-venue market data & signals pillar hub.