Continuous play in historical racing devices

A system for wagering during a wagering period, the system comprising:

• a wagering base comprising a first plurality of pools each with an outcome accessed by an input wager to entitle a bettor to a return;
• a plurality of terminals at which wagers are input, each directed to access an outcome in one of the pools;
• and
• a processing system configured to process the input wagers in a manner whereby each input wager either:
• a) accesses;
• or b) fails to access an outcome in the pool to which each input wager is directed,
• the processing system further configured so that there is an initial pre-assigned probability of accessing the outcome of each pool through an input wager directed to each pool,
• the processing system further configured to identify a collective return by determining the number of input wagers that have accessed an outcome in a particular pool to which those wagers were directed,
• the processing system further configured to change the wagering base after the wagering period has begun and before the wagering period is concluded based upon one or more system operating parameters detected during the wagering period.