Year	Number
1993	7.4588661037
1994	8.4882187374
1995	7.981584238
1996	8.9104141536
1997	8.8171290712
1998	8.7745074387
1999	8.7318858062
2000	8.7089827101
2001	8.6586248492
2002	8.3770808203
2003	8.0955367913
2004	7.8139927624
2005	7.5324487334
2006	7.0593687173
2007	6.5862887012
2008	6.1132086852
2009	5.6401286691
2010	5.2975472457
2011	5.3136308806
2012	6.3803779654
2013	7.6992360273
2014	7.4238037797
2015	3.7072778448
2016	4.271411339
2017	4.8486696301
2018	4.9577804584
2019	4.2340168878
2020	3.4740651387