"Over the three years after a firm began offering a health plan with a deductible of at least $500, its spending for a set of 24 low-value outpatient services fell by an average of 13.7% compared to firms that never offered such a plan.... The percent reductions in spending were significantly larger for low-value services than for all outpatient care and all laboratory services, suggesting some ability and willingness of patients to selectively curtail low-value care."