44 USC 3506
I believe the Commerce Dept. is an agency.  Does the census form inform us if the information being collected is mandatory  or voluntary?
GP
44 USC  3506
 
(c) With respect to the  collection of information and the control of paperwork, each agency shall—  
(1) establish a  process within the office headed by the Chief Information Officer designated  under subsection (a), that is sufficiently independent of program responsibility  to evaluate fairly whether proposed collections of information should be  approved under this subchapter, to— 
(A) review each  collection of information before submission to the Director for review under  this subchapter, including— 
(B) ensure that  each information collection— 
(ii) indicates  the collection is in accordance with the clearance requirements of section 3507;  and 
March 20, 2010