Year % 1997 20.5980066445183 1998 20.5980066445183 1999 20.5980066445183 2001 20.5980066445183 2002 20.5980066445183 2003 20.5980066445183 2004 21.1038961038961 2005 21.1038961038961 2006 20.7792207792208 2007 21.3114754098361 2008 22.0779220779221 2009 22.0779220779221 2010 22.0779220779221 2011 24.7557003257329 2012 24.6753246753247 2013 24.6753246753247 2014 25.0814332247557 2015 26.0355029585799 2016 26.0355029585799 2017 26.2686567164179 2018 26.9461077844311 2019 28.9940828402367 2020 28.9940828402367 2021 30.4733727810651 2022 30.4733727810651 2023 30.6547619047619