Year % 1997 26.1904761904762 1998 26.1904761904762 1999 30.9417040358744 2000 30.9417040358744 2001 31.0810810810811 2002 32.1724709784411 2003 32.1724709784411 2004 32.75 2005 31.7589576547231 2006 31.5960912052117 2007 31.6476345840131 2008 32.1895424836601 2009 32.7974276527331 2010 32.7974276527331 2011 32.9032258064516 2012 32.9032258064516 2013 36.4500792393027 2014 36.4500792393027 2015 36.4500792393027 2016 36.4500792393027 2017 30.7475317348378 2018 30.7475317348378 2019 30.8885754583921 2020 31.1706629055007 2021 34.9184782608696 2022 34.9184782608696 2023 35.1902173913043