| Year | Value | | 2022 | 9.507657429728 | | 2021 | 4.2593641754287 | | 2020 | 2.8981937602627 | | 2019 | 2.3775873278977 | | 2018 | 3.214539254891 | | 2017 | 3.4885482537127 | | 2016 | 3.0382064350688 | | 2015 | 2.0764779016518 | | 2014 | 2.2359740790468 | | 2013 | 3.4335852683074 | | 2012 | 5.9120060249116 | | 2011 | 5.4420247048784 | | 2010 | 3.4805076373585 | | 2009 | 4.0754808012017 | | 2008 | 11.581075174825 | | 2007 | 4.61743772242 | | 2006 | 6.7399306038751 | | 2005 | 7.2855064049092 | | 2004 | 3.2824422094908 | | 2003 | 5.4882536340708 | | 2002 | 4.7057912374603 | | 2001 | 5.3708029338044 | | 2000 | 3.8226008808631 | | 1999 | 4.843531588264 | | 1998 | 5.9765085214186 | | 1997 | 7.087005912057 | | 1996 | 11.477528598287 | | 1995 | 18.235168327484 | | 1994 | 30.136169035471 | | 1993 | 10.376449926359 | | 1992 | 10.527444011959 | | 1991 | 11.896095301125 |
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