The Constitution has provisions for proportional representation. So when a large shift occurs from one area to another, the number of representatives in said areas either decreases or increases. Districts get redrawn to handle to movement of people. This allows for the government to better keep proper proportional representation current. This is the reason that census are so important. The amount of data that it collected, especially regarding representation, is vital to better handling of issues. The recent announcement about adding the citizenship question can be seen as a shrewd political move. This could cause many people to not participate out of fear of deportation, even though the only required questions are names and how many people live in the residence. Everything after that is optional.
