Year Percent 1961 55.31915 1962 55.31915 1963 55.31915 1964 55.31915 1965 55.31915 1966 55.31915 1967 55.31915 1968 55.31915 1969 55.31915 1970 55.31915 1971 53.19149 1972 53.19149 1973 51.06383 1974 51.06383 1975 51.06383 1976 48.93617 1977 48.93617 1978 48.93617 1979 48.93617 1980 48.93617 1981 48.93617 1982 48.93617 1983 48.93617 1984 48.93617 1985 48.93617 1986 48.93617 1987 48.93617 1988 48.93617 1989 48.93617 1990 48.93617 1991 48.93617 1992 48.93617 1993 48.93617 1994 48.93617 1995 48.93617 1996 48.93617 1997 48.93617 1998 48.93617 1999 48.93617 2000 48.93617 2001 48.40426 2002 48.61702 2003 48.6383 2004 48.53191 2005 46.38298 2006 46.34043 2007 44.19149 2008 44.17021 2009 44.19149 2010 42.06383 2011 42.06383 2012 39.91489 2013 40.02128 2014 40 2015 40.02128 2016 40.04255 2017 40.04255 2018 40.07234 2019 40.00021 2020 39.9517 2021 39.90681