"Most 12th graders felt that they would be little affected personally by the legalization of either the sale or the use of marijuana. Over half (56%) of the respondents said that they would not use the drug even if it were legal to buy and use, while others indicated they would use it about as often as they do now (15%) or less often (1.5%). Only 9% said they would use it more often than they do at present, while 10% thought they would try it. Another 9% said they did not know how their behavior would be affected if marijuana were legalized. Still, this amounts to 19% of all seniors, or about one in five, who thought that they would try marijuana, or that their use would increase, if marijuana were legalized."
Johnston, L. D., O’Malley, P. M., Bachman, J. G., Schulenberg, J. E. & Miech, R. A. (2014). Monitoring the Future national survey results on drug use, 1975–2013: Volume I, Secondary school students. Ann Arbor: Institute for Social Research, The University of Michigan.