Year Percent
1950 3.138
1951 2.935
1952 2.597
1953 2.378
1954 2.253
1955 2.201
1956 2.202
1957 2.24
1958 2.302
1959 2.378
1960 2.467
1961 2.57
1962 2.692
1963 2.837
1964 2.994
1965 3.155
1966 3.301
1967 3.404
1968 3.445
1969 3.429
1970 3.38
1971 3.324
1972 3.28
1973 3.253
1974 3.241
1975 3.234
1976 3.216
1977 3.174
1978 3.099
1979 2.997
1980 2.89
1981 2.795
1982 2.7
1983 2.589
1984 2.469
1985 2.347
1986 2.24
1987 2.196
1988 2.251
1989 2.395
1990 2.58
1991 2.754
1992 2.894
1993 2.994
1994 3.052
1995 3.088
1996 3.119
1997 3.125
1998 3.085
1999 3.006
2000 2.915
2001 2.833
2002 2.759
2003 2.688
2004 2.624
2005 2.558
2006 2.495
2007 2.489
2008 2.581
2009 2.759
2010 2.975
2011 3.171
2012 3.287
2013 3.29
2014 3.19
2015 3.043
2016 2.903
2017 2.793
2018 2.717
2019 2.676
2020 2.65
2021 2.621
2022 2.587
2023 2.556
2024 2.525
2025 2.495
2026 2.468
2027 2.442
2028 2.417
2029 2.392
2030 2.368
2031 2.344
2032 2.321
2033 2.297
2034 2.275
2035 2.252
2036 2.229
2037 2.205
2038 2.181
2039 2.156
2040 2.13
2041 2.104
2042 2.077
2043 2.05
2044 2.023
2045 1.995
2046 1.968
2047 1.94
2048 1.913
2049 1.886
2050 1.859
2051 1.832
2052 1.806
2053 1.779
2054 1.752
2055 1.726
2056 1.7
2057 1.674
2058 1.651
2059 1.629
2060 1.608
2061 1.587
2062 1.565
2063 1.544
2064 1.521
2065 1.499
2066 1.477
2067 1.455
2068 1.434
2069 1.413
2070 1.392
2071 1.371
2072 1.35
2073 1.329
2074 1.308
2075 1.286
2076 1.265
2077 1.243
2078 1.222
2079 1.201
2080 1.18
2081 1.159
2082 1.138
2083 1.117
2084 1.096
2085 1.076
2086 1.055
2087 1.035
2088 1.014
2089 0.994
2090 0.974
2091 0.954
2092 0.934
2093 0.914
2094 0.894
2095 0.875
2096 0.856
2097 0.837
2098 0.818
2099 0.799