| Year | Value | | 2022 | 2.2789988129115 | | 2021 | 2.0061859141127 | | 2020 | 2.1013336180248 | | 2019 | 2.2144190826307 | | 2018 | 1.6149375961106 | | 2017 | 1.8375075266196 | | 2016 | 1.7451557271187 | | 2015 | 1.8260863364821 | | 2014 | 1.9407687642611 | | 2013 | 1.90065993167 | | 2012 | 1.9709936557384 | | 2011 | 2.0036450286792 | | 2010 | 2.085965341946 | | 2009 | 2.1572764584746 | | 2008 | 2.1297981120665 | | 2007 | 2.2505171700029 | | 2006 | 2.1706211990569 | | 2005 | 2.2739435740814 | | 2004 | 2.9731615637403 | | 2003 | 3.4479084710202 | | 2002 | 4.2099541062492 | | 2001 | 4.0275711979198 | | 2000 | 5.1539431901456 | | 1999 | 4.0059474345167 | | 1998 | 3.5118979788457 | | 1997 | 3.7865044666184 | | 1996 | 3.5112858951201 |
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