"Spending patterns over two years were best described by classifying patients into five groups: minimal users comprised 11 percent of the population; low-, moderate- and high-cost patients accounted for 15, 25, and 41 percent, respectively; and patients with rising costs were 8 percent of the population.... Across patients with similar baseline spending, the odds of subsequently incurring rising spending were higher for patients using fewer medications, having fewer office visits, seeing a larger number of different physicians and using tobacco. These factors suggest patients to target for intervention."