Year	Number
1996	12.56274
1997	9.81697
1999	11.51385
2000	11.14499
2001	12.92319
2002	17.03945
2003	18.26892
2004	14.01443
2005	15.44325
2006	16.64885
2007	16.26811
2008	17.34978
2009	18.96388
2010	18.87385
2011	19.92376
2012	19.89882
2013	20.2092
2014	19.71697
2015	20.25954
2017	18.89359
2018	23.08864