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The source provides the following information: "Family income is expressed as a percentage of the federal poverty level (FPL), which was calculated from the family’s income in the previous calendar year and family size using the U.S. Census Bureau’s poverty thresholds. Walking for leisure was based on a yes response to the survey question, “Sometimes you may walk for fun, relaxation, exercise, or to walk the dog. In the past 7 days, did you walk for any of these reasons?” Estimates are based on household interviews of a sample of the U.S. civilian noninstitutionalized population."