The Hamilton method, used from 1850 until 1900, is the simplest. In this method, an 'ideal' district size is determined by dividing the US population by 435 (the number of seats). The state populations are then divided by this ideal size to find their deserved fraction of seats. In 2000, for example, California was entitled to a quota of 52.44 seats. The states are then ordered by the size of their fractional remainders. Those with the biggest remainder are the first to be rounded up and given an extra representative. Remaining seats are distributed, down the list, until all 435 seats are meted out.

The other methods round up or down without regard to rank. But this can easily result in a total of more or less than 435 seats. So then the 'ideal' district size is adjusted and the numbers re-crunched until the right number of seats comes out of the mix.

These methods — Jefferson, Webster and the current one, Huntington-Hill, which has been in effect since the 1940 census — use different rounding points. For example, the Huntington-Hill method rounds up or down from the geometric mean of the nearest integers (so if California deserves 52.44 seats it is rounded down, as the geometric mean of 52 and 53 is 52.4976). Since the geometric mean is proportionally larger for higher numbers, the current method has an inherent bias towards giving small states a boost up — something Edelman and others have criticized.

Edelman's method is instead designed to minimize the difference between the most over-represented state and the most under-represented one, in terms of the difference between the actual number of people per representative and the ideal number. This is done through an iterative process that evaluates 385 scenarios to find this minimum total deviation. He argues that this comes closest to matching the ideal of “one person, one vote”.

Using his method for populations in 2000, Montana, Delaware, South Dakota, Utah and Mississippi would each gain one seat; Texas, New York, Florida, Ohio and North Carolina would lose one; and California would lose three. “That could very well freak people out,” says Edelman.