Year % (national estimate) 1960 5.863192182410423 1966 7.198323678047578 1973 5.5456626812515895 1975 6.614335349375884 1976 7.95243403939056 1977 8.735167886897248 1978 10.561056105610561 1979 10.562805872756933 1980 10.05844773684926 1981 12.152777777777777 1982 12.08540630182421 1983 22.129032258064516 1984 23.68006304176517 1986 12.652693840812654 1989 41.793334263003764 1990 36.53504577128023 1991 31.107031911889298 1992 32.21248940378638 1993 30.39000274649822 1994 31.037277147487842 1995 29.439825541774567 1996 18.695203713254255 1998 27.342657342657343 1999 27.6428280635093 2000 29.86897623806351 2001 29.392039655926517 2002 26.813282842994468 2005 30.717041372888122 2006 29.39621591541458 2007 32.30125523012552 2008 30.030411943599667 2009 31.55020926300618 2010 30.790085205267236 2011 30.12291495577485 2012 30.31451820360417 2013 31.247102457116366 2014 31.794808166866563 2015 32.14442726873059 2016 32.939638202796104 2017 32.82634730538923 2018 27.06602406788682 2019 23.19006373590456 2020 21.336178157087613 2021 22.200193913433573 2022 21.677432407046144