Year | Value | 2021 | 19.43415122684 | 2020 | 19.414121181773 | 2019 | 19.394091136705 | 2018 | 19.374061091638 | 2017 | 19.35403104657 | 2016 | 19.173760640961 | 2015 | 19.178768152228 | 2014 | 19.187781672509 | 2013 | 19.196795192789 | 2012 | 19.20580871307 | 2011 | 19.21482223335 | 2010 | 18.911330049261 | 2009 | 19.085714285714 | 2008 | 19.260098522167 | 2007 | 19.434482758621 | 2006 | 19.608866995074 | 2005 | 19.783251231527 | 2004 | 19.95763546798 | 2003 | 20.132019704433 | 2002 | 20.306403940887 | 2001 | 20.48078817734 | 2000 | 20.655172413793 | 1999 | 20.612807881773 | 1998 | 20.570443349754 | 1997 | 20.528078817734 | 1996 | 20.485714285714 | 1995 | 20.443349753695 | 1994 | 20.400985221675 | 1993 | 20.358620689655 | 1992 | 20.316256157636 | 1991 | 20.273891625616 | 1990 | 20.231527093596 |
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