| Year | Value | | 2021 | 1.9003611837983 | | 2020 | 1.9003611837983 | | 2019 | 1.9003611837983 | | 2018 | 1.9003611837983 | | 2017 | 1.9003611837983 | | 2016 | 1.9003611837983 | | 2015 | 1.9003611837983 | | 2014 | 1.9003611837983 | | 2013 | 1.9003611837983 | | 2012 | 1.8995210904402 | | 2011 | 1.8995210904402 | | 2010 | 1.8995210904402 | | 2009 | 1.8979093755756 | | 2008 | 1.8830738276517 | | 2007 | 1.8814733520818 | | 2006 | 1.8798728765119 | | 2005 | 1.878272400942 | | 2004 | 1.8766719253721 | | 2003 | 1.8750714498022 | | 2002 | 1.8734709742323 | | 2001 | 1.8718704986625 | | 2000 | 1.8702700230926 | | 1999 | 1.8670690719528 | | 1998 | 1.863868120813 | | 1997 | 1.8606671696733 | | 1996 | 1.8574662185335 | | 1995 | 1.8542652673937 | | 1994 | 1.851064316254 | | 1993 | 1.8478633651142 | | 1992 | 1.8446624139744 | | 1991 | 1.8414614628347 | | 1990 | 1.8382605116949 |
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