Year | Value | 2021 | 16.181890265867 | 2020 | 15.21308263134 | 2019 | 15.229528537403 | 2018 | 15.275639585158 | 2017 | 15.740221702075 | 2016 | 15.374072681623 | 2015 | 15.448099904281 | 2014 | 15.329238520969 | 2013 | 15.157775429355 | 2012 | 14.727848469725 | 2011 | 14.616747790886 | 2010 | 14.232578646611 | 2009 | 14.083665353866 | 2008 | 15.656504701129 | 2007 | 16.178798735512 | 2006 | 16.085939442959 | 2005 | 15.640135251016 | 2004 | 14.960868946801 | 2003 | 14.934516523247 | 2002 | 15.199683256947 | 2001 | 16.341225615643 | 2000 | 16.987590248442 | 1999 | 16.410458374461 | 1998 | 16.232420424079 | 1997 | 15.817554124478 | 1996 | 15.577726553089 | 1995 | 15.306056826086 | 1994 | 14.703810732326 | 1993 | 14.119172316327 | 1992 | 14.16230422355 | 1991 | 14.547870816438 | 1990 | 14.537167084006 | 1989 | 14.527698046361 | 1988 | 14.560862601357 | 1987 | 14.72051266834 | 1986 | 14.377093938467 | 1985 | 14.374765253805 | 1984 | 14.131083552161 | 1983 | 14.212058218788 | 1982 | 14.935152620622 | 1981 | 15.07727710844 | 1980 | 14.800437016701 | 1979 | 14.538360779437 | 1978 | 14.36443608248 | 1977 | 14.451146184673 | 1976 | 14.029500349424 | 1975 | 13.942636088405 | 1974 | 14.285849805385 | 1973 | 13.833501935238 | 1972 | 14.175067109021 |
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