Year scale 1-100 1970 47.8515625 1971 48.59375 1972 49.2578125 1973 50.37109375 1974 50.80078125 1975 51.40625 1976 51.97265625 1977 52.3828125 1978 52.63671875 1979 53.28125 1980 53.53515625 1981 54.609375 1982 55.05859375 1983 55.9375 1984 56.62109375 1985 57.2265625 1986 57.40234375 1987 57.48046875 1988 58.6328125 1989 59.2578125 1990 60.41015625 1991 60.859375 1992 61.81640625 1993 62.40234375 1994 63.75 1995 64.4921875 1996 65.15625 1997 66.85546875 1998 67.6953125 1999 68.69140625 2000 69.8828125 2001 70.68359375 2002 71.93359375 2003 72.40234375 2004 72.734375 2005 72.83203125 2006 73.37890625 2007 73.92578125 2008 74.70703125 2009 75.33203125 2010 75.60546875 2011 75.60546875 2012 75.859375 2013 76.71875 2014 77.24609375 2015 78.22265625 2016 78.61328125 2017 78.9453125 2018 79.3359375 2019 79.62890625 2020 80.234375 2021 80.41015625 2022 80.6640625 2023 81.15234375