Year	Number of
1990	7.21
1991	7.72
1992	8.3
1993	8.91
1994	9.6
1995	10.37
1996	11.08
1997	11.79
1998	12.47
1999	13.15
2000	13.8
2001	14.35
2002	14.94
2003	15.54
2004	16.55
2005	18.17
2006	20.21
2007	23.2
2008	26.89
2009	30.96
2010	35.86
2011	39.11
2012	42.13
2013	45.26
2014	48.75
2015	53
2016	57.71