Within most security exchanges, an order book system is used. The order book will typically be visible to all market participants. The order book displays unmatched buy and sell limit orders for a particular security. Unmatched limit orders are orders which have a price limit attached to them, which represents the highest price a buyer is willing to pay or the lowest price a seller is willing to sell for but which haven't yet found a corresponding buy or sell order at a common price to be matched with yet. These unmatched orders will remain on the order book until an equivalent corresponding trade is entered into the system. The unmatched buy orders or bids are ranked from highest to lowest price since the higher the price someone is willing to pay, the greater the likelihood of finding a matching sell order. For the same reason, the sell orders or offers are ranked from lowest to highest. Orders of equal price are ranked by the time the order was entered with earlier orders having priority. The security to which this order book relates would be said to have a bid offer of 105 to 107, meaning a seller can sell at 105 right now if they want to since an unmatched buy order exists at that price. Equally, buyers can buy at 107 now if they want to since an unmatched sell order exists at that price. Bid offer spreads tend to be tighter on exchange-driven platforms than the bid offer spreads quoted by market makers in quote-driven markets due to higher levels of liquidity. This order book process is only true for electronic or screen-based exchanges. There are a small number of exchanges that still operate through open outcry with traders agreeing orders verbally on a face-to-face basis, although that is a very small percentage of stock exchanges.