As a trader, you want to know that there are mechanisms in place to ensure an orderly market. A regulated marketplace like CME Group provides this order by setting price limits and price banding.
Price limits are the maximum price range permitted for a futures contract in each trading session. These price limits are measured in ticks and vary from product to product. When markets hit the price limit, different actions occur depending on the product being traded. Some markets may temporarily halt until price limits can be expanded or trading may be stopped for the day based on regulatory rules. Different futures contracts will have different price limit rules; i.e. Equity Index futures have different rules than Agricultural futures.
Equity Indexes futures have a three level expansion: 7%, 13% and 20% to the downside, and a 7% limit up and down in overnight trading.
When price reaches any of those levels the market will go limit up or limit down.
Price limits are re-calculated daily and remain in effect for all trading days except in certain physically-deliverable markets, where price limits are lifted prior to expiration so that futures prices are not prevented from converging on prices for the underlying commodity.
Typically, Agricultural futures will go limit up or down most often compared to Equity Index futures which very rarely if ever go limit up or down. When trading a specific product, it is important to be aware of price limits and the mechanisms that occur when limits are hit. Traders also know that it is possible for limits to be reached for more than one session in a row, however the expansion of limit thresholds over the last few years have reduced this occurrence.
Price banding is a similar mechanism which subjects all orders to price validation and rejects orders outside the given band to maintain orderly markets. Bands are calculated dynamically for each product based on the last price, plus or minus a fixed band value. Thus, if markets quickly move in one direction, the price bands dynamically adjust to accommodate new trading ranges.
The rules for each market can be found on cmegroup.com.
It is important to note that traders can place trades outside the daily price limits. These trades will be executed when price limits and price bands move within the specified range. So, traders still have the ability to place good-til-canceled or good-til-date orders inside and outside daily price limits.
In the last few years there are fewer and fewer times that markets will actually go limit up or down, but it is important to be aware of these pricing rules when you trade.