Year Number 1996 2.12765955924988 1998 0.531914889812469 2000 8.99470901489258 2002 3.17460322380066 2003 4.52261304855347 2004 8.73786449432373 2005 11.1650485992432 2006 8.69565200805664 2007 15.4589376449585 2008 10.5769233703613 2009 9.00473976135254 2010 12.3222751617432 2011 15.1658763885498 2012 16.1137447357178 2013 19.9052124023438 2014 23.8095245361328 2015 20.4761905670166 2016 21.9047622680664 2017 19.5238094329834 2018 18.3962268829346 2019 16.5094337463379 2020 18.3962268829346 2021 18.3962268829346 2022 16.9811325073242