Year % 1997 18.1159420289855 1998 18.1159420289855 1999 17.921146953405 2000 17.7935943060498 2001 24.6710526315789 2002 24.6710526315789 2003 24.6710526315789 2004 23.9344262295082 2005 23.9344262295082 2006 29.8192771084337 2007 30.7228915662651 2008 30.7228915662651 2009 31.4814814814815 2010 31.2883435582822 2011 34.9740932642487 2012 34.9740932642487 2013 34.9740932642487 2014 34.9740932642487 2015 34.9740932642487 2016 33.4894613583138 2017 34.2984409799555 2018 34.2984409799555 2019 34.8583877995643 2020 34.8583877995643 2021 33.8129496402878 2022 33.8129496402878 2023 33.8129496402878