Year years 1960 66.507 1961 66.487 1962 66.238 1963 66.507 1964 67.006 1965 66.624 1966 66.489 1967 66.063 1968 65.906 1969 65.18 1970 64.908 1971 65.168 1972 65.049 1973 65.127 1974 64.895 1975 64.699 1976 64.737 1977 64.281 1978 64.119 1979 63.757 1980 63.537 1981 63.766 1982 63.963 1983 64.022 1984 63.658 1985 64.078 1986 65.858 1987 66.3 1988 66.4 1989 66.1 1990 65.6 1991 64.62 1992 63.81 1993 63.16 1994 62.39 1995 61.22 1996 61.52 1997 62.23 1998 63.17 1999 62.62 2000 62.1 2001 62.32 2002 62.7 2003 62.64 2004 62.6 2005 62.23 2006 62.38 2007 62.51 2008 62.51 2009 63.79 2010 65.28 2011 65.98 2012 66.11 2013 66.34 2014 66.25 2015 66.37 2016 66.73 2017 67.02 2018 66.69 2019 66.92 2020 66.39 2021 65.16 2022 63.525