Year Percent
1950 0.929
1951 0.931
1952 0.929
1953 0.915
1954 0.892
1955 0.864
1956 0.833
1957 0.802
1958 0.773
1959 0.747
1960 0.722
1961 0.696
1962 0.665
1963 0.626
1964 0.579
1965 0.529
1966 0.482
1967 0.441
1968 0.407
1969 0.383
1970 0.364
1971 0.348
1972 0.339
1973 0.342
1974 0.355
1975 0.373
1976 0.391
1977 0.411
1978 0.437
1979 0.467
1980 0.493
1981 0.512
1982 0.519
1983 0.514
1984 0.495
1985 0.472
1986 0.444
1987 0.376
1988 0.236
1989 0.028
1990 -0.216
1991 -0.458
1992 -0.661
1993 -0.799
1994 -0.867
1995 -0.898
1996 -0.922
1997 -0.915
1998 -0.845
1999 -0.716
2000 -0.545
2001 -0.366
2002 -0.218
2003 -0.136
2004 -0.124
2005 -0.151
2006 -0.181
2007 -0.209
2008 -0.243
2009 -0.28
2010 -0.32
2011 -0.367
2012 -0.414
2013 -0.456
2014 -0.491
2015 -0.523
2016 -0.554
2017 -0.579
2018 -0.591
2019 -0.59
2020 -0.58
2021 -0.568
2022 -0.558
2023 -0.551
2024 -0.548
2025 -0.547
2026 -0.544
2027 -0.542
2028 -0.541
2029 -0.541
2030 -0.542
2031 -0.544
2032 -0.546
2033 -0.551
2034 -0.557
2035 -0.564
2036 -0.572
2037 -0.579
2038 -0.585
2039 -0.59
2040 -0.594
2041 -0.598
2042 -0.602
2043 -0.607
2044 -0.612
2045 -0.618
2046 -0.623
2047 -0.628
2048 -0.634
2049 -0.639
2050 -0.645
2051 -0.65
2052 -0.655
2053 -0.66
2054 -0.665
2055 -0.669
2056 -0.673
2057 -0.678
2058 -0.681
2059 -0.684
2060 -0.687
2061 -0.689
2062 -0.691
2063 -0.693
2064 -0.694
2065 -0.696
2066 -0.696
2067 -0.696
2068 -0.696
2069 -0.695
2070 -0.693
2071 -0.69
2072 -0.687
2073 -0.683
2074 -0.678
2075 -0.673
2076 -0.666
2077 -0.66
2078 -0.653
2079 -0.647
2080 -0.64
2081 -0.634
2082 -0.627
2083 -0.62
2084 -0.613
2085 -0.606
2086 -0.599
2087 -0.592
2088 -0.585
2089 -0.578
2090 -0.572
2091 -0.566
2092 -0.56
2093 -0.554
2094 -0.548
2095 -0.543
2096 -0.538
2097 -0.533
2098 -0.529
2099 -0.525