Year % 1997 7.8740157480315 1998 7.8740157480315 1999 7.8740157480315 2000 20.5298013245033 2001 20.5298013245033 2002 20.5298013245033 2004 21.7105263157895 2005 21.7105263157895 2006 21.7105263157895 2007 20.9150326797386 2008 20.9150326797386 2009 23.5294117647059 2010 23.5294117647059 2011 23.841059602649 2012 23.841059602649 2013 23.841059602649 2014 23.841059602649 2015 15.2317880794702 2016 12.5827814569536 2017 18.5430463576159 2018 18.5430463576159 2019 20.5298013245033 2020 31.1258278145695 2021 31.1258278145695 2022 31.7880794701987 2023 31.7880794701987