13 The smaller variation in U.S. postal densities is due to differences in the quality of delivery service which dampen the impact of low population density on many routes.
US postal density varies 65% between rural and urban areas.
mnli hypothesis: US postal density varies 65% between rural and urban areas. premise: 13 The smaller variation in U.S. postal densities is due to differences in the quality of delivery service which dampen the impact of low population density on many routes.