Year years 1960 54.53502130587183 1961 55.141455142103915 1962 55.83191856857115 1963 56.451815243013364 1964 56.661139689728394 1965 57.70647953232738 1966 58.17890625648616 1967 58.7203744210699 1968 59.168299694827276 1969 59.41039599781395 1970 59.823680022366375 1971 60.19277842916316 1972 60.46180396728959 1973 60.42949665534349 1974 61.01216765441315 1975 61.045945070891 1976 61.66045360795063 1977 61.911104942702444 1978 62.36044827195945 1979 62.74066079680094 1980 62.8499762791294 1981 63.04117442954247 1982 63.24433810266118 1983 63.65552048060602 1984 64.09659580742624 1985 64.52004527956275 1986 64.63559730728625 1987 64.92031946571167 1988 65.25944493305856 1989 65.42753887523908 1990 65.70301232038635 1991 65.87955546278243 1992 66.09130680672897 1993 66.27283445088106 1994 66.47968641538894 1995 66.7313986981694 1996 66.9085682484442 1997 67.03747250459925 1998 67.23718662653644 1999 67.3133507965179 2000 67.30394872813139 2001 67.41204517686421 2002 67.20526610886374 2003 67.51969951296707 2004 67.68820691006113 2005 67.83041239032006 2006 67.98573346419435 2007 67.96521287191078 2008 68.12384038417777 2009 68.02361266641945 2010 68.395698405641 2011 68.53138451670908 2012 68.59709178317786 2013 68.62577394946096 2014 68.64263989416597 2015 68.56220876131903 2016 68.82751123689447 2017 69.11886489235842 2018 69.21374828616389 2019 69.29425140877008 2020 69.36492110040345 2021 69.16359418284318 2022 69.73483483939496