Year % 1997 9.54545454545455 1998 15.4545454545455 1999 15.4545454545455 2000 15.4545454545455 2001 15.4545454545455 2002 15.4545454545455 2003 15.4545454545455 2004 15 2005 15 2006 15 2007 15 2008 37.2727272727273 2009 38.6363636363636 2010 38.6363636363636 2011 38.1818181818182 2012 34.0909090909091 2013 34.0909090909091 2014 36.8181818181818 2015 36.8181818181818 2016 36.8181818181818 2017 30.4545454545455 2018 30.4545454545455 2019 30 2020 30 2021 29.5454545454545 2022 33.6363636363636 2023 33.6363636363636