Year % 2006 3.95454002794938 2007 3.05938058506971 2008 4.33679547147844 2009 4.73959731629681 2010 3.66354687451701 2011 2.93741700834833 2012 3.28720316567911 2013 3.39335992951502 2014 3.27080240326135 2015 3.05632098417855 2016 2.92120388061596 2017 2.3628317385567 2018 2.145224364129 2019 2.2621650345564 2020 3.06942035880795 2021 2.68848835667779