Year | Value | 2021 | 7.8781040571191 | 2020 | 7.7106015217608 | 2019 | 7.5025875520056 | 2018 | 7.6739980000767 | 2017 | 7.8601063705155 | 2016 | 8.0519344366473 | 2015 | 8.3188404216632 | 2014 | 8.5553948896487 | 2013 | 8.8199980895672 | 2012 | 9.1228442471647 | 2011 | 9.451676522809 | 2010 | 9.9456262304964 | 2009 | 10.122445964151 | 2008 | 10.532884620162 | 2007 | 10.907237434747 | 2006 | 11.303105153387 | 2005 | 11.783816622427 | 2004 | 12.20538365462 | 2003 | 12.571768992445 | 2002 | 12.990152656907 | 2001 | 13.357025751371 | 2000 | 13.709728627642 | 1999 | 14.252921899881 | 1998 | 14.812116905929 | 1997 | 14.832683880269 | 1996 | 15.113702899202 | 1995 | 15.263971278958 | 1994 | 16.800711657836 | 1993 | 15.991437813086 | 1992 | 16.57934384591 | 1991 | 16.680192246673 | 1990 | 16.592711168284 | 1989 | 16.682295805398 | 1988 | 17.568773467599 | 1987 | 17.38335117985 | 1986 | 18.145100994579 | 1985 | 18.85066997982 | 1984 | 19.199806470392 | 1983 | 19.142625399726 | 1982 | 18.117081242227 | 1981 | 18.310204172683 | 1980 | 18.54655409266 | 1979 | 18.832867894101 | 1978 | 19.142069993588 | 1977 | 19.286796191836 | 1976 | 19.564810578342 | 1975 | 20.155051493156 | 1974 | 20.460646878824 | 1973 | 20.474409837635 | 1972 | 21.107164664905 | 1971 | 20.912248750892 | 1970 | 21.179899794651 | 1969 | 21.435475007548 | 1968 | 21.642045587922 | 1967 | 21.908017080479 | 1966 | 22.460189948198 | 1965 | 22.417779348749 | 1964 | 22.577972793807 | 1963 | 22.940037391501 | 1962 | 23.086664065399 | 1961 | 23.537455031926 | 1960 | 23.818587102738 |
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