The constitution set up the system of using a census every 10 years to count the population for representatives.
Representation by population is the idea that the number of representatives your state has is dependent on the amount of people in the state.
Representation in the US senate is not based on population. Each state has two senators. The House's representation is based on population.
virginia plan
dick
The number of Representatives from each state is based on the population of that state.
The population of a state really affects the representation in Congress. In fact, change in represention all depends on the population. So, to answer your question, every time there is a big change in the population that is when the representation changes.
The compromise provided for a bicameral federal legislature that used a dual system of representation: the upper house would have equal representation from each state, while the lower house would have proportional representation based on a state's population.
virginia plan
d. two houses: representation based on state population, and representation based on state land mass
The Great Compromise
House of reps
House of Representatives