Year | Value | 2022 | 21.443842980156 | 2021 | 21.195864154104 | 2020 | 21.050206694618 | 2019 | 21.237082587618 | 2018 | 21.02378970036 | 2017 | 20.936288883384 | 2016 | 20.864704468247 | 2015 | 20.742866463333 | 2014 | 20.686653500656 | 2013 | 20.578303076157 | 2012 | 20.412255392226 | 2011 | 20.353783348681 | 2010 | 20.319007876464 | 2009 | 20.367447677685 | 2008 | 20.461410313818 | 2007 | 20.438365627373 | 2006 | 20.420896591454 | 2005 | 20.45036617848 | 2004 | 20.439887791786 | 2003 | 20.377756178572 | 2002 | 20.345954558657 | 2001 | 20.183140354032 | 2000 | 20.084952766803 | 1999 | 19.953335843787 | 1998 | 19.887958251222 | 1997 | 19.797151243073 | 1996 | 19.710375099262 | 1995 | 19.597790973679 | 1994 | 19.67453354858 | 1993 | 19.446121703735 | 1992 | 19.435025943509 | 1991 | 19.427164784529 |
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