Numbers alone don't always capture the full picture. This is particularly true when it comes to reporting water use.
Water use is typically reported in gallons per capita per day (GPCD), which is calculated by dividing water use by the population, divided by 365 (the number of days in a year). GPCD is helpful in estimating future water demand and tracking conservation achievements, but it is not an effective measurement to compare water use efficiencies.
Most cities and states calculate GPCD differently. And, GPCD does not account for climate and demographic differences.