thumb|350px|Histogram of travel time (to work), US 2000 census. Area under the curve equals 1. This diagram uses Q/total/width (crowding) from the table. The height of a block represents crowding which is defined as - percentage per horizontal unit.
thumb|350px|Histogram of travel time (to work), US 2000 census. Area under the curve equals 1. This diagram uses Q/total/width (crowding) from the table The height of a block represents crowding which is defined as - percentage per horizontal unit.