Due to the success of the mailout/mailback questionnaire in 1970, the program was expanded for 1980 with about 95 percent of the U.S. population being enumerated in this manner. Despite the widespread use of the mail to deliver and return questionnaires, the U.S. Census Bureau still employed approximately 459,000 enumerators to enumerate hard-to-reach populations and households that did not return their questionnaires.