Year scale 1-100 1970 17.5 1971 17.5 1972 17.5 1973 17.5 1974 17.5 1975 17.5 1976 17.5 1977 17.5 1978 17.5 1979 17.5 1980 17.5 1981 17.5 1982 17.5 1983 17.5 1984 17.5 1985 17.5 1986 17.5 1987 17.5 1988 17.5 1989 17.5 1990 17.5 1991 23.75 1992 23.75 1993 23.75 1994 23.75 1995 23.75 1996 23.75 1997 26.25 1998 26.25 1999 26.25 2000 26.25 2001 26.25 2002 26.25 2003 26.25 2004 26.25 2005 26.25 2006 26.25 2007 26.25 2008 26.25 2009 29.375 2010 29.375 2011 29.375 2012 29.375 2013 29.375 2014 29.375 2015 29.375 2016 29.375 2017 29.375 2018 29.375 2019 29.375 2020 32.5 2021 32.5 2022 32.5 2023 32.5