| Year | Value | | 2022 | 12.774146363761 | | 2021 | 3.1496062992127 | | 2020 | 1.9369412669422 | | 2019 | 2.6645613342543 | | 2018 | 2.5140371288381 | | 2017 | 1.3119458822323 | | 2016 | 0.52001019627827 | | 2015 | 0.32521977742767 | | 2014 | 0.076165329541987 | | 2013 | 1.4004736896303 | | 2012 | 3.6061026352289 | | 2011 | 3.9192859914629 | | 2010 | 0.95701813297514 | | 2009 | 1.6151046405824 | | 2008 | 4.5981797632503 | | 2007 | 2.7567237163814 | | 2006 | 4.4833312044961 | | 2005 | 2.7090849458838 | | 2004 | 7.5485008818342 | | 2003 | 8.5541430540665 | | 2002 | 3.1271422298461 | | 2001 | 7.3296201911553 | | 2000 | 12.03578059743 | | 1999 | 10.570441607523 | | 1998 | 6.6656512319582 | | 1997 | 6.1419899959565 | | 1996 | 5.7758278615595 | | 1995 | 9.8410957983775 | | 1994 | 13.415520342225 | | 1993 | 23.287027664545 | | 1992 | 9.8935051977117 |
|