Year % 1997 7.15596330275229 1998 8.10313075506446 1999 8.44036697247707 2000 9.00735294117647 2001 8.83977900552486 2002 8.83977900552486 2003 8.83977900552486 2004 8.25688073394496 2005 8.28729281767956 2006 8.25688073394496 2007 9.05730129390018 2008 9.05730129390018 2009 10.8256880733945 2010 10.8256880733945 2011 11.0091743119266 2012 11.0091743119266 2013 11.0091743119266 2014 11.4180478821363 2015 11.9705340699816 2016 11.9705340699816 2017 11.8081180811808 2018 11.8081180811808 2019 14.3911439114391 2020 14.3646408839779 2021 14.4444444444444 2022 14.9446494464945 2023 15.2416356877323