Year scale 1-100 1970 45.7039473684211 1971 45.9210526315789 1972 46.2631578947368 1973 47.1414473684211 1974 47.6118421052632 1975 48.0197368421053 1976 48.3815789473684 1977 48.7467105263158 1978 49.4407894736842 1979 49.7269736842105 1980 50.0131578947368 1981 50.4703947368421 1982 50.8486842105263 1983 51.2532894736842 1984 51.6348684210526 1985 51.9539473684211 1986 52.2763157894737 1987 52.5032894736842 1988 53.0822368421053 1989 53.3947368421053 1990 54.0197368421053 1991 54.4276315789474 1992 54.9769736842105 1993 55.5559210526316 1994 56.3190789473684 1995 57.0559210526316 1996 57.8388157894737 1997 58.6480263157895 1998 59.2072368421053 1999 59.9276315789474 2000 60.6480263157895 2001 61.1085526315789 2002 61.9605263157895 2003 62.9013157894737 2004 63.9769736842105 2005 65.0131578947368 2006 65.9276315789474 2007 66.9309210526316 2008 67.8717105263158 2009 68.8782894736842 2010 69.5427631578947 2011 70.0657894736842 2012 70.6546052631579 2013 71.4506578947368 2014 71.9243421052632 2015 72.4605263157895 2016 73.0822368421053 2017 73.6973684210526 2018 74.4013157894737 2019 75.2894736842105 2020 75.9934210526316 2021 76.6085526315789 2022 77.1184210526316 2023 77.8552631578947