How often must Congress update its voting districts?

Congress must update its voting districts every 10 years because this process is tied to the decennial census, which occurs every ten years. After the census, states are required to redraw their congressional and state legislative district lines to reflect population changes and ensure equal representation for all citizens. This practice is mandated by the Constitution to uphold the principle of "one person, one vote," ensuring that districts are fairly apportioned based on the most current population data. This regular updating helps account for shifts in population, urbanization, and demographic changes, making the electoral process more representative of the current population. The other options do not align with the legal requirements established for redistricting, as annual or more frequent updates are not necessary or mandated.