Complex sentence: The United States Constitution requires a decennial census for the purpose of assuring a fair distribution of seats in the U.S. House of Representatives, and this has generally occurred without incident, with the exception of the 1920 Census.
Split into simpler sentences: The United States Constitution requires a decennial census for the purpose of assuring a fair distribution of seats in the U.S. House of Representatives. This has generally occurred without incident, with the exception of the 1920 Census.