Year years 1960 46.125 1961 46.948 1962 47.575 1963 48.304 1964 49.169 1965 50.193 1966 51.316 1967 52.394 1968 53.465 1969 54.324 1970 54.95 1971 55.322 1972 48.626 1973 55.725 1974 55.85 1975 56.036 1976 56.299 1977 56.243 1978 53.571 1979 50.813 1980 57.914 1981 58.198 1982 58.605 1983 56.794 1984 56.131 1985 56.501 1986 57.775 1987 57.66 1988 60.3 1989 62.475 1990 63.096 1991 63.931 1992 64.266 1993 64.685 1994 65.181 1995 65.608 1996 66.052 1997 66.515 1998 65.209 1999 67.12 2000 67.234 2001 67.215 2002 67.18 2003 67.217 2004 67.423 2005 67.936 2006 68.725 2007 69.559 2008 70.586 2009 71.433 2010 72.009 2011 72.416 2012 72.615 2013 72.704 2014 72.812 2015 72.983 2016 73.256 2017 73.554 2018 73.85 2019 74.054 2020 71.795 2021 73.837 2022 74.615