| Year | Value | | 2022 | 2.7871140518037 | | 2021 | 2.5845397670781 | | 2020 | 2.0919979226568 | | 2019 | 2.4266259778279 | | 2018 | 2.4655735614885 | | 2017 | 2.7744842331799 | | 2016 | 3.2554401892803 | | 2015 | 3.6498273421263 | | 2014 | 3.2741011426946 | | 2013 | 4.2799859148427 | | 2012 | 5.0234770046092 | | 2011 | 5.7292156917443 | | 2010 | 8.2994170328049 | | 2009 | 7.2047621380798 | | 2008 | 8.8819931575035 | | 2003 | 6.4164108720075 | | 2000 | 7.4544700006707 | | 1999 | 6.7198720745536 | | 1998 | 8.5284375483234 |
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