Year Number 1996 13.8297872543335 1998 7.44680833816528 2000 2.64550256729126 2002 8.99470901489258 2003 3.01507544517517 2004 4.36893224716187 2005 7.76699018478394 2006 10.1449279785156 2007 13.043478012085 2008 15.865385055542 2009 21.3270149230957 2010 20.3791465759277 2011 20.8530807495117 2012 25.5924167633057 2013 28.4360198974609 2014 30 2015 24.2857151031494 2016 32.3809509277344 2017 28.0952377319336 2018 26.4150943756104 2019 26.8867931365967 2020 28.301887512207 2021 27.3584899902344 2022 29.2452831268311