The actual Enumeration shall be made within three years after the first meeting of the Congress and within every subsequent term of ten years in such manner as they shall by law direct. Before seats are allocated, however, the total number of seats in the legislative body is often determined. But this is not always the approach adopted. In its first 120 years, for example, the U.S. House of Representatives simply grew in size to accommodate new states and a rapidly growing population. From 1790 to 1900, seats were allocated to states on the basis of a population quota which, despite its gradual increase over time, resulted in the House of Representatives expanding in size from 106 to 391 during this time period.
Many countries still allow the legislature to grow as the population of the country increases.
In the United States, however, a permanent ceiling on membership in the House of Representatives was set at 435 legislators in 1910. Seats were allocated by first giving each state one seat and then awarding the remaining seats in succession to the states with the largest remaining quota. In 1950, the statute defining the formula was modified slightly. Each state was given one seat, and the remaining 385 seats were allocated in succession under a priority numbers formula. Although the process is a mechanical one, the formula for the allocation of seats has not escaped controversy.