Year Percent
1950 3.433
1951 3.36
1952 3.217
1953 3.089
1954 2.988
1955 2.923
1956 2.905
1957 2.94
1958 3.029
1959 3.162
1960 3.317
1961 3.46
1962 3.555
1963 3.578
1964 3.533
1965 3.458
1966 3.385
1967 3.314
1968 3.236
1969 3.155
1970 3.075
1971 3
1972 2.935
1973 2.885
1974 2.851
1975 2.824
1976 2.804
1977 2.798
1978 2.818
1979 2.859
1980 2.897
1981 2.92
1982 2.951
1983 3.014
1984 3.097
1985 3.191
1986 3.265
1987 3.24
1988 3.061
1989 2.749
1990 2.379
1991 2.033
1992 1.759
1993 1.582
1994 1.502
1995 1.472
1996 1.45
1997 1.45
1998 1.499
1999 1.59
2000 1.706
2001 1.828
2002 1.936
2003 2.015
2004 2.065
2005 2.098
2006 2.129
2007 2.161
2008 2.191
2009 2.22
2010 2.245
2011 2.261
2012 2.263
2013 2.248
2014 2.217
2015 2.177
2016 2.134
2017 2.087
2018 2.035
2019 1.981
2020 1.925
2021 1.868
2022 1.812
2023 1.758
2024 1.705
2025 1.653
2026 1.604
2027 1.561
2028 1.525
2029 1.497
2030 1.473
2031 1.451
2032 1.432
2033 1.418
2034 1.407
2035 1.398
2036 1.389
2037 1.379
2038 1.367
2039 1.352
2040 1.335
2041 1.318
2042 1.298
2043 1.272
2044 1.242
2045 1.209
2046 1.175
2047 1.141
2048 1.107
2049 1.073
2050 1.038
2051 1.004
2052 0.971
2053 0.94
2054 0.912
2055 0.884
2056 0.858
2057 0.833
2058 0.811
2059 0.791
2060 0.774
2061 0.757
2062 0.74
2063 0.725
2064 0.709
2065 0.694
2066 0.68
2067 0.664
2068 0.649
2069 0.632
2070 0.615
2071 0.597
2072 0.579
2073 0.56
2074 0.54
2075 0.519
2076 0.499
2077 0.478
2078 0.458
2079 0.439
2080 0.421
2081 0.403
2082 0.385
2083 0.368
2084 0.352
2085 0.337
2086 0.323
2087 0.308
2088 0.295
2089 0.283
2090 0.27
2091 0.258
2092 0.246
2093 0.234
2094 0.221
2095 0.208
2096 0.194
2097 0.181
2098 0.167
2099 0.152