It has long been common to identify an agent's degrees of belief with her betting rates. Here is this betting interpretation (BI) in a nutshell: A bet on a proposition A with price C and a non-zero stake S (= the monetary prize to be won by the bettor if A is true) is said to be fair for an agent iff the latter is willing to take each side of the bet, to buy the bet as to sell it. Assuming that such a bet on A exists and that the C/S ratio is constant for different fair bets on A, this ratio is the agent's betting rate for A.