Year	Number of
1990	7.65
1991	8.12
1992	8.65
1993	9.22
1994	9.86
1995	10.58
1996	11.22
1997	11.89
1998	12.54
1999	13.19
2000	13.82
2001	14.35
2002	14.94
2003	15.74
2004	16.95
2005	18.68
2006	20.81
2007	24.08
2008	27.63
2009	31.71
2010	36.71
2011	40.03
2012	43.16
2013	46.4
2014	50.08
2015	54.6
2016	59.68