Read the passage. Paragraph 1: A city offered rebates for low-flow showerheads but saw little change in water use. Surveys showed that many residents had received the devices but left them in closets. Paragraph 2: The program was redesigned so plumbers installed the showerheads during routine inspections and explained how to adjust the settings. The policy worked better when incentives were connected to ordinary household habits. Paragraph 3: Water use fell modestly in neighborhoods where installations were completed. Which statement best describes the main idea of paragraph 2, rather than just a detail from it?