These types of studies are not very believable. At least, not to me. Taking surveys and asking people about their consumption is just not very accurate and way too subjective.
Based on interviews with more than 40,000 California households conducted by the California Health Interview Survey (CHIS), the study, "Still Bubbling Over: California Adolescents Drinking More Soda and Other Sugar-Sweetened Beverages," provides a comprehensive look at youth (2- to 17-year-olds) consumption of sugary drinks, charting consumption patterns from 2005–07 to 2011–12
The study, which also provides county-by-county youth consumption rates, was produced collaboratively by the UCLA Center for Health Policy Research and the California Center for Public Health Advocacy.
And honestly, it's none of their damn business.