According to various embodiments, trades may be filled based at in part on order price and fill rates determined for providers of orders. In some embodiments, orders at a given price in an order book may be ordered in order of decreasing fill rate, such that orders associated with a higher fill rate (or higher probability of fill) are preferenced above orders associated with a lower fill rate. In some embodiments, order books may also be ordered based in part on response times from order providers. For example, orders in an order book may be ordered according to an algorithm that preferences higher fill rates and shorter response times ahead of orders with lower fill rates and longer response times. Order book ordering algorithms may also consider order quantity and interdependence and duplication of order quantity.