Year Percent 1960 0.1329 1961 5.92934 1962 8.34007 1963 6.2456 1964 23.60955 1965 28.19127 1966 40.07275 1967 38.16628 1968 49.19801 1969 85.70947 1970 49.26986 1971 75.79332 1972 52.59039 1973 50.11885 1974 87.2631 1975 91.44542 1976 83.10589 1977 37.38155 1978 38.04751 1979 31.66352 1980 23.4577 1981 43.44071 1982 61.90797 1983 76.73044 1984 342.93491 1985 162.08319 1986 137.4857 1987 136.29832 1988 85.48981 1989 99.97941 1990 97.78688 1991 93.02603 1992 123.91249 1993 169.7858 1994 148.22498 1995 98.31008 1996 71.4357 1997 106.74472 1998 75.61137 1999 65.889 2000 71.0111 2001 76.68092 2002 72.69414 2003 101.73724 2004 116.75324 2005 61.71913 2006 57.52082 2007 53.08383 2008 31.89282 2009 22.48248 2010 28.93004 2011 23.24472 2012 32.24763 2013 26.24363 2014 27.15751 2015 27.75012 2016 33.28164 2017 42.08832 2018 35.24682 2019 36.41104 2020 49.25411 2021 43.17993