Year	Number of
1990	5.52
1991	5.94
1992	6.3
1993	6.62
1994	6.93
1995	7.25
1996	8.05
1997	9.03
1998	10.22
1999	11.58
2000	13.13
2001	13.67
2002	14.32
2003	15.5
2004	17.81
2005	21.77
2006	23.79
2007	27.43
2008	32.02
2009	36.83
2010	41.42
2011	46.36
2012	50.54
2013	54.07
2014	57.09
2015	59.83
2016	65.57