| Year | Value | | 2022 | 19.705046151839 | | 2021 | 4.6835442090345 | | 2020 | 1.1998944498357 | | 2019 | 2.3345093798803 | | 2018 | 2.6979277920839 | | 2017 | 3.7228886230371 | | 2016 | 0.90552507546034 | | 2015 | 0.8840974055006 | | 2014 | 0.10375800943371 | | 2013 | 1.0474793706534 | | 2012 | 3.0899827705542 | | 2011 | 4.1302756264508 | | 2010 | 1.3192136205546 | | 2009 | 4.4530445651854 | | 2008 | 10.925885624166 | | 2007 | 5.7371738279984 | | 2006 | 3.7391200406066 | | 2005 | 2.6584848406526 | | 2004 | 1.1641025210467 | | 2003 | -1.1343085499025 | | 2002 | 0.28150661034558 | | 2001 | 1.3671203081782 | | 2000 | 0.9816154788576 | | 1999 | 0.72755062655742 | | 1998 | 5.0675538584197 | | 1997 | 8.8810484846589 | | 1996 | 24.62519538645 | | 1995 | 39.647629032829 | | 1994 | 72.254681616443 | | 1993 | 410.45185856132 | | 1992 | 1,020.6205652435 |
|