1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021   2020 -
2021
Change		   2016 -
2021
Change		 Proportional
Change		   Peak year -
2021
Change		 Proportional
Change		   Low year -
2021
Change		 Proportional
Change
Last 30 Days 8th Grade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 3.3 1.9 1.6 1.6 1.6 1.4 0.8 | -0.5 |   -55.4 | -2.5*** -75.1 | 0.0 0.0
  10th Grade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 3.8 3.0 3.0 3.1 2.6 2.4 1.2 | -1.2* |   -60.4 | -3.3*** -73.2 | 0.0 0.0
  12th Grade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 7.8 6.1 6.6 5.8 4.9 § 1.8 | . |   -70.4 | -6.0*** -76.8 | . .

Source: The Monitoring the Future study, the University of Michigan.
The peak year prevalence is noted in BOLD. The lowest prevalence after the peak is underlined.
*** = p < 0.001 ** = p < 0.01 * = p < 0.05