Year | Value | 2022 | 19.914646681864 | 2021 | 19.610209092197 | 2020 | 19.366119510997 | 2019 | 19.597776586989 | 2018 | 19.481876778942 | 2017 | 19.28596214363 | 2016 | 19.112380640002 | 2015 | 19.07457884219 | 2014 | 18.887024780396 | 2013 | 18.721055325943 | 2012 | 18.475060922037 | 2011 | 18.036614265743 | 2010 | 17.637688373718 | 2009 | 17.38757832191 | 2008 | 16.92677604494 | 2007 | 16.479876961988 | 2006 | 16.088161157404 | 2005 | 15.806022806967 | 2004 | 15.730551379896 | 2003 | 15.603133825798 | 2002 | 15.776092222061 | 2001 | 16.082172994874 | 2000 | 15.890736238677 | 1999 | 15.724139186435 | 1998 | 15.519193972575 | 1997 | 15.351100375891 | 1996 | 15.146920386024 | 1995 | 15.008610669703 | 1994 | 14.923973162049 | 1993 | 14.904199692789 | 1992 | 14.903687362253 | 1991 | 14.93035288911 |
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