Year years 1960 42.071 1961 42.18 1962 42.483 1963 42.704 1964 42.905 1965 43.148 1966 43.364 1967 43.575 1968 43.778 1969 43.975 1970 44.164 1971 44.353 1972 44.547 1973 44.738 1974 42.471 1975 42.832 1976 43.216 1977 45.529 1978 45.43 1979 45.92 1980 46.105 1981 46.283 1982 46.443 1983 46.782 1984 47.078 1985 46.922 1986 47.014 1987 47.525 1988 39.87 1989 43.209 1990 43.572 1991 24.904 1992 26.114 1993 49.196 1994 48.885 1995 49.092 1996 48.946 1997 48.779 1998 49.247 1999 49.093 2000 49.272 2001 49.339 2002 49.334 2003 49.147 2004 49.034 2005 49.176 2006 49.022 2007 48.88 2008 49.456 2009 50.298 2010 48.669 2011 49.625 2012 51.248 2013 51.97 2014 52.267 2015 52.855 2016 52.887 2017 53.577 2018 54.283 2019 55.122 2020 53.967 2021 53.246 2022 54.072