During the last decade, lifetime value (LTV) has become the standard method for measuring the success of customer marketing programs. Return on investment is used for campaigns, and profitability is used, particularly in banks, to take a snap shot of the performance of existing customers. Lifetime value, unlike these other measurements, predicts the future performance of a group of customers, based on their past and current spending behavior. It also permits you to evaluate the performance and value of the firm as a whole. It is particularly useful for those who do extensive e-mailing to their customers.