1. A computer-implemented method of order allocation, the computer-implemented method comprising: establishing an inner market representing a first portion of an order book at a computer-implemented trading host, wherein the inner market is defined as a function of an inner market parameter; establishing an outer market at the computer-implemented trading host, wherein the outer market represents a second portion of the order book that includes the remainder of the order book not represented by the inner market of the order book; allocating, via a FIFO allocation processor, a first portion of an incoming order to the inner market utilizing a first-in, first-out (FIFO) algorithm; and allocating, via a pro-rata allocation processor, a second portion, in excess of the first portion, of the incoming order to the outer market using a pro-rata algorithm.