(ACORN) was given a contract to help publicize the importance of the census count and to encourage individuals to fill out their forms. In September 2009, after controversial undercover videos showing four ACORN staffers giving tax advice to a man and a woman posing as a prostitute, the bureau canceled ACORN's contract. Various American celebrities, including Demi Lovato and Eva Longoria, were used in public service announcements targeting younger people to fill out census forms. Wilmer Valderrama and Rosario Dawson have helped spread census awareness among young Hispanics, a historically low participating ethnicity in the U.S. census. Rapper Ludacris also participated in efforts to spread awareness of the 2010 census. The Census Bureau hired about 635,000 people to find those U.S. residents who had not returned their forms by mail; as of May 28, 2010, 113 census workers had been victims of crime while conducting the census. As of June 29, there were 436 incidents involving assaults or threats against enumerators, more than double the 181 incidents in 2000; one enumerator, attempting to hand-deliver the census forms to a Hawaii County police officer, was arrested for trespassing – the officer's fellow policemen made the arrest. Some political conservatives and libertarians questioned the validity of the questions and even encouraged people to refuse to answer questions for privacy and constitutional reasons. Michele Bachmann, a former conservative Republican Representative from Minnesota, stated that she would not fill out her census form other than to indicate the number of people living in her household because "the Constitution doesn't require any information beyond that." Former Republican representative and Libertarian presidential candidate Bob Barr stated that the census has become too intrusive, going beyond the mere enumeration (i.e., count) intended by the framers of the U.S. Constitution. According to political commentator Juan Williams, "Census participation rates have been declining since 1970, and if conservatives don't participate, doubts about its accuracy and credibility may become fatal." As a result, the Census Bureau undertook an unprecedented advertising campaign targeted at encouraging white political conservatives to fill out their forms, in the hope of avoiding an undercount of this group. The 2010 U.S. census was the primary sponsor at NASCAR races in Atlanta, Bristol, and Martinsville, and sponsored the No. 16 Ford Fusion driven by Greg Biffle for part of the season, because of a marketing survey that indicated most NASCAR fans lean politically conservative. It also ran