Year | Value | 2021 | 8.3157648751203 | 2020 | 7.7114630556418 | 2019 | 6.495258064951 | 2018 | 6.4527627016578 | 2017 | 6.3803619267267 | 2016 | 6.3471487441358 | 2015 | 6.197180891836 | 2014 | 6.0989027797666 | 2013 | 6.0748987446961 | 2012 | 6.072318262055 | 2011 | 6.0511706089326 | 2010 | 6.195403392208 | 2009 | 5.9866704097396 | 2008 | 5.9574229522855 | 2007 | 5.9489373620205 | 2006 | 5.8868841145517 | 2005 | 5.867523611316 | 2004 | 5.9312203360068 | 2003 | 5.9784260173044 | 2002 | 5.9492962207481 | 2001 | 6.0036607441797 | 2000 | 6.0262598718072 | 1999 | 6.0706158996417 | 1998 | 6.1586447288563 | 1997 | 6.1828115301424 | 1996 | 6.2515962409704 | 1995 | 6.3383112191264 | 1994 | 6.3957115695902 | 1993 | 6.5055111742117 | 1992 | 6.598985610649 | 1991 | 6.7034838317088 | 1990 | 6.8298485363558 | 1989 | 6.9187646443075 | 1988 | 7.0395343584426 | 1987 | 7.1988493164038 | 1986 | 7.3707317977195 | 1985 | 7.6190661046922 | 1984 | 7.766394204528 | 1983 | 7.9452306595671 | 1982 | 8.2038320703768 | 1981 | 8.3396554793538 | 1980 | 8.5644644733011 | 1979 | 8.7365228970792 | 1978 | 8.881501058256 | 1977 | 9.0374419149935 | 1976 | 9.3092124737521 | 1975 | 9.3908083340948 | 1974 | 9.6518926593684 | 1973 | 9.8593318092626 | 1972 | 10.138736674308 | 1971 | 10.330763156621 | 1970 | 10.818583513976 | 1969 | 10.864496350585 | 1968 | 11.091614334473 | 1967 | 11.350062373424 | 1966 | 11.624735399745 | 1965 | 11.916251195851 | 1964 | 12.202705173502 | 1963 | 12.538697904632 | 1962 | 12.827240855721 | 1961 | 13.145008716151 | 1960 | 13.528153175866 |
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