| Year | Value | | 2021 | 0.066678101783212 | | 2020 | 0.043808326946324 | | 2019 | 0.053989073663036 | | 2018 | 0.072010299012475 | | 2017 | 0.066314394480061 | | 2016 | 0.070834556204716 | | 2015 | 0.084964568718348 | | 2014 | 0.091133486171974 | | 2013 | 0.069710679067115 | | 2012 | 0.10809415537982 | | 2011 | 0.019334709532694 | | 2010 | 0.024066973283343 | | 2009 | 0.01982815306599 | | 2008 | 0.015761536141927 | | 2007 | 0.018079452608023 | | 2006 | 4.0025286744309 | | 2005 | 3.9226578637682 | | 2004 | 3.513688568561 | | 2003 | 3.2754555628767 | | 2002 | 3.2086591631197 | | 2001 | 3.313760743443 | | 2000 | 3.9759733851763 | | 1999 | 5.2884231089317 | | 1998 | 8.5916752572041 | | 1997 | 9.9667148328622 | | 1996 | 13.968941910993 | | 1995 | 14.548597204949 | | 1994 | 11.14196646123 | | 1993 | 17.03390948674 | | 1992 | 10.355901243297 | | 1991 | 3.4183521958623 | | 1990 | 3.5958587539286 |
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