Year | Value | 2021 | 13.124740811808 | 2020 | 12.771607272177 | 2019 | 13.153737246101 | 2018 | 13.013949567868 | 2017 | 13.989444345881 | 2016 | 13.309664664842 | 2015 | 13.139774529861 | 2014 | 13.556557134403 | 2013 | 13.271250080871 | 2012 | 13.580668735704 | 2011 | 13.105721951265 | 2010 | 12.785823969104 | 2009 | 12.954926530085 | 2008 | 13.754391446936 | 2007 | 12.820428195921 | 2006 | 11.831022176603 | 2005 | 11.577027401832 | 2004 | 11.604511579824 | 2003 | 12.446074163859 | 2002 | 12.688739339799 | 2001 | 14.585519151497 | 2000 | 14.855789084744 | 1999 | 14.53171740654 | 1998 | 14.031025635843 | 1997 | 15.312341085021 | 1996 | 15.897367157372 | 1995 | 15.76850364726 | 1994 | 16.613152278789 | 1993 | 16.290333945719 | 1992 | 16.103353501287 | 1991 | 15.181531598059 | 1990 | 14.546269592565 | 1989 | 15.687873622744 | 1988 | 14.072012621579 | 1987 | 13.078079891107 | 1986 | 12.735769464966 | 1985 | 15.662167056589 | 1984 | 17.663382090754 | 1983 | 18.760838719849 | 1982 | 18.916341977329 | 1981 | 17.88020558777 | 1980 | 16.992918328849 | 1979 | 16.039770684729 | 1978 | 15.934647223707 | 1977 | 16.724555438691 | 1976 | 15.996374155191 | 1975 | 16.571124724118 | 1974 | 15.06460713562 | 1973 | 14.785101389049 | 1972 | 14.550184888525 |
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