Year	Number
1994	16.07731
1995	16.45064
1996	15.80605
1997	16.71574
1998	18.37664
1999	17.3652
2000	18.08057
2001	19.27347
2002	19.2308
2003	18.49942
2004	18.72526
2005	18.4976
2006	18.33587
2007	17.57331
2008	17.25366
2009	17.24437
2010	17.13356
2011	17.27053
2012	17.49129
2013	19.81995
2014	19.68648
2015	19.22038
2016	18.86585
2017	18.64141
2018	18.56649