Year | Value | 2021 | 13.760245901639 | 2020 | 13.852459016393 | 2019 | 13.975409836066 | 2018 | 14.089417555373 | 2017 | 14.323659111886 | 2016 | 14.576003446543 | 2015 | 15.02899071271 | 2014 | 15.149337986247 | 2013 | 15.353191139942 | 2012 | 15.642791080053 | 2011 | 15.310217100525 | 2010 | 15.504115226337 | 2009 | 15.825262724088 | 2008 | 16.135684091143 | 2007 | 16.477507222452 | 2006 | 16.711395540875 | 2005 | 16.964377903975 | 2004 | 17.072918818426 | 2003 | 17.138429752066 | 2002 | 17.295175121397 | 2001 | 17.459168906347 | 2000 | 17.810491395397 | 1999 | 17.613518556915 | 1998 | 17.706821480406 | 1997 | 17.851959361393 | 1996 | 18.090400165872 | 1995 | 18.484345842836 | 1994 | 19.127099315779 | 1993 | 19.438109060751 | 1992 | 19.676549865229 | 1991 | 19.977192618702 | 1990 | 20.246734397678 | 1989 | 20.505909185155 | 1988 | 20.702882023637 | 1987 | 20.806551938627 | 1986 | 20.77545096413 | 1985 | 20.827285921625 | 1984 | 20.910221853618 | 1983 | 21.065726726104 | 1982 | 21.241965581588 | 1981 | 21.262699564586 | 1980 | 21.356002488078 | 1979 | 21.44930541157 | 1978 | 21.55297532656 | 1977 | 21.428571428571 | 1976 | 21.356002488078 | 1975 | 21.366369479577 | 1974 | 21.511507360564 | 1973 | 21.718847190545 | 1972 | 21.812150114037 | 1971 | 22.123159859009 | 1970 | 22.320132697491 | 1969 | 22.351233671988 | 1968 | 22.537839518972 | 1967 | 22.765913331951 | 1966 | 22.67261040846 | 1965 | 22.423802612482 | 1964 | 21.677379224549 | 1963 | 20.837652913125 | 1962 | 20.713249015136 | 1961 | 21.076093717603 |
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