context: From 2000 to 2012, consumption of cigars more than doubled in the United States, from slightly over 6.1 billion in 2000 to more than 13.7 billion in 2012. Cigar use is most common among young people. In the 2012 National Youth Tobacco Survey data, the Centers for Disease Control and Prevention (CDC) estimated that 12.6% of high school students had smoked at least one cigar in the past 30 days. After cigarettes, cigars were the second most commonly used tobacco product in youths and the most commonly used tobacco product among African American high school students. From the CDC’s national Adult Tobacco Survey for 2009-2015, data suggest that prevalence among adults was highest among 18-24 years (15.9%) followed by 25-44 years old (7.2%). From the same survey, prevalence among men (10.4%) was significantly higher than women (3.1%) and likewise among LGBT (12.2%) and heterosexual (6.5%) respondents. The National Survey on Drug Use and Health (2015) indicated that 12.5 million American (over age 12) smoked a cigar product in the past month and over 24 million smoked a cigar product in the past year.  As reported in other surveys,  use was more common among most often among men than women and more prevalent among African- Americans and Native Americans than among white Americans.
question: Over how many years was the consumption of cigars in the US slightly over 6.1 billion?
answer: 12