| Year | Value | | 2021 | 9.794253597875 | | 2020 | 9.5149992858083 | | 2019 | 9.9957560747909 | | 2018 | 10.075058576684 | | 2017 | 9.9564744137239 | | 2016 | 9.5590633366044 | | 2015 | 9.6422746972935 | | 2014 | 9.7451763796532 | | 2013 | 8.9293625676154 | | 2012 | 9.4577783512196 | | 2011 | 9.36683510297 | | 2010 | 8.8712134760668 | | 2009 | 8.3275828169992 | | 2008 | 8.0940722999316 | | 2007 | 7.8378778913988 | | 2006 | 8.3505041827766 | | 2005 | 8.2647645044043 |
|