| Year | Value | | 2022 | 1.5061430058026 | | 2021 | 1.5436946491781 | | 2020 | 1.6733871062548 | | 2019 | 1.5795347937518 | | 2018 | 1.5905157428377 | | 2017 | 1.6350421585302 | | 2016 | 1.6864201379658 | | 2015 | 1.7048987707396 | | 2014 | 1.654346679302 | | 2013 | 1.6386924925107 | | 2012 | 1.5971836228576 | | 2011 | 1.5439345852397 | | 2010 | 1.5966241941775 | | 2009 | 1.7553753091813 | | 2008 | 1.6004228294032 | | 2007 | 1.6288093982588 | | 2006 | 1.6842820722599 | | 2005 | 1.701642708985 | | 2004 | 1.7769457417474 | | 2003 | 1.8437305558251 | | 2002 | 1.8538183166274 | | 2001 | 1.7985499598669 | | 2000 | 1.6741271848418 | | 1999 | 1.749000973946 | | 1998 | 1.630159805722 | | 1997 | 1.7186914938813 | | 1996 | 1.7565559456455 | | 1995 | 1.81906447351 | | 1994 | 1.8796753112531 | | 1993 | 1.9798230170101 | | 1992 | 2.334910446592 | | 1991 | 2.2789469095538 | | 1990 | 2.3511421502027 | | 1989 | 2.3861721233058 |
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