| Year | Value | | 2019 | 4.6401926807958 | | 2018 | 5.4940352071889 | | 2017 | 5.4363858940098 | | 2016 | 5.2840040816961 | | 2015 | 4.6675823557404 | | 2013 | 2.5718640612902 | | 2012 | -1.1707256681848 | | 2011 | 7.4506150627345 | | 2010 | 1.6069491925453 | | 2009 | 0.27760319853048 | | 2008 | 1.1013314123736 | | 2007 | 117.51526112424 |
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