Year	Number
1993	15.16787
1994	15.08177
1995	15.22061
1996	14.80619
1997	15.44541
1998	16.61645
1999	16.06912
2000	16.42786
2001	17.17534
2002	17.25652
2003	16.85155
2004	17.00315
2005	16.8431
2006	16.79332
2007	16.26311
2008	16.09906
2009	16.04701
2010	15.98421
2011	16.09995
2012	16.27819
2013	17.9494
2014	17.93834
2015	17.60635
2016	17.33722
2017	17.15356
2018	17.15988