Year years 1960 43.452 1961 43.563 1962 43.877 1963 44.1 1964 44.3 1965 44.544 1966 44.76 1967 44.97 1968 45.173 1969 45.37 1970 45.557 1971 45.747 1972 45.94 1973 46.131 1974 43.818 1975 44.182 1976 44.568 1977 46.918 1978 46.95 1979 47.305 1980 47.489 1981 47.666 1982 47.83 1983 48.166 1984 48.459 1985 48.281 1986 48.37 1987 48.903 1988 43.835 1989 46.717 1990 47.105 1991 26.565 1992 27.312 1993 50.648 1994 50.327 1995 50.6 1996 50.447 1997 50.195 1998 50.66 1999 50.525 2000 50.66 2001 50.74 2002 50.731 2003 50.614 2004 50.538 2005 50.661 2006 50.597 2007 50.515 2008 51.12 2009 51.853 2010 50.563 2011 51.304 2012 53.161 2013 53.843 2014 54.277 2015 54.857 2016 55.044 2017 55.654 2018 56.375 2019 57.078 2020 55.967 2021 55.28 2022 56.107