As National Census Day April 1 inches closer, US residents will begin receiving 2010 US Census questionnaires in their mailboxes beginning in March. Under the US Constituion a national census is completed every ten years to get an accurate picture of the nations growing and changing population and demographics. Every resident of the United States and Puerto Rico including citizens and non-citizens, is required by law to complete a 2010 Census form to account for everyone living at their household address as of Aptil 1, 2010.