1. A method of predicting outcomes of marketing campaigns comprising more than one campaign step, the method comprising: predicting a number of responses to be received if a first campaign step were performed toward a first target group of customers, each customer having a response probability; selecting a second target group from the first target group using the response probabilities, the second target group being substantially equal to the predicted number of responses; and predicting an outcome of performing a second campaign step toward the second target group.