"• The number of persons aged 12 or older who smoked cigarettes for the first time within the past 12 months was approximately 2.3 million in 2012, which was similar to the estimates from 2004 through 2011 (ranging from 2.1 million to 2.5 million), but was higher than the estimates for 2002 and 2003 (1.9 million and 2.0 million, respectively) (Figure 5.7). The 2012 estimate averages to about 6,400 new cigarette smokers every day. About half of new cigarette smokers in 2012 (51.4 percent) initiated prior to age 18.
"• In 2002 and 2012, the numbers of cigarette initiates who were younger than age 18 when they first used were similar (1.3 million and 1.2 million, respectively). However, the number of cigarette initiates who began smoking at age 18 or older increased from 623,000 in 2002 to 1.1 million in 2012.
"• In 2012, among recent initiates aged 12 to 49, the average age of first cigarette use was 17.8 years, which was higher than the corresponding average age in 2011 (17.2 years).
"• Of those aged 12 or older who had not smoked cigarettes prior to the past year (i.e., those at risk for initiation), the past year initiation rate for cigarettes was 2.3 percent in 2012, which was similar to the rate in 2011 (2.4 percent).
"• Among youths aged 12 to 17 who had not smoked cigarettes prior to the past year (i.e., youths at risk for initiation), the incidence rate in 2012 was 4.8 percent, which was lower than the 2011 rate (5.5 percent). However, past year initiation rates in 2012 of 4.7 percent for males aged 12 to 17 and 4.8 percent for females in this age group who had never smoked prior to the past year were not significantly different from corresponding rates in 2011 (5.4 percent for males and 5.5 percent for females) (Figure 5.8). Past year initiation rates in 2012 among males and females aged 12 to 17 who were at risk for initiation of cigarette use were lower than the rates in 2002 to 2010."

Source

Substance Abuse and Mental Health Services Administration, Results from the 2012 National Survey on Drug Use and Health: Summary of National Findings, NSDUH Series H-46, HHS Publication No. (SMA) 13-4795. Rockville, MD: Substance Abuse and Mental Health Services Administration, 2013, pp. 60-61.
http://www.samhsa.gov/data/NS…
http://www.samhsa.gov/data/NS…