totaled 1.9 million households. By the show's tenth anniversary in 1979, nine million American children under the age of 6 were watching Sesame Street daily. According to a 1993 survey conducted by the U.S. Department of Education, out of the show's 6.6 million viewers, 2.4 million kindergartners regularly watched it. 77% of preschoolers watched it once a week, and 86% of kindergartners and first- and second-grade students had watched it once a week before starting school. The show reached most young children in almost all demographic groups. The show's ratings significantly decreased in the early 1990s, due to changes in children's viewing habits and in the television marketplace. The producers responded by making large-scale structural changes to the show. By 2006, Sesame Street had become "the most widely viewed children's television show in the world," with 20 international independent versions and broadcasts in over 120 countries. A 1996 survey found that 95% of all American preschoolers had watched the show by the time they were three years old. In 2008, it was estimated that 77 million Americans had watched the series as children. By the show's 40th anniversary in 2009, it was ranked the fifteenth-most-popular children's show on television, and by its 50th anniversary in 2019, the show had 100% brand awareness globally. In 2018, the show was the second-highest-rated program on PBS Kids. In 2021, however, the Sesame Street documentary "50 Years of Sunny Days," which was broadcast nationally on ABC, did not fare well in the ratings, scoring only approximately 2.3 million viewers. Influence , there were over 1,000 research studies regarding Sesame Streets efficacy, impact, and effect on American culture. The CTW solicited the Educational Testing Service (ETS) to conduct summative research on the show. ETS's two "landmark" summative evaluations, conducted in 1970 and 1971, demonstrated that the show had a significant educational impact on its viewers. These studies have been cited in other studies of the effects of television on young children. Additional studies conducted throughout Sesame Streets history demonstrated that the show continued to have a positive effect on its young viewers. Lesser believed that Sesame Street research "may have conferred a new respectability upon the studies of the effects of visual media upon children." He also believed that the show had the same effect on the prestige of producing shows for children in the television industry. Historian Robert Morrow, in his book Sesame Street