Year	Number of
1990	7.04
1991	7.47
1992	7.91
1993	8.42
1994	8.89
1995	9.3
1996	9.7
1997	10.01
1998	10.26
1999	10.55
2000	10.94
2001	11.48
2002	12.21
2003	13.19
2004	14.19
2005	15.14
2006	17
2007	18.98
2008	21.35
2009	23.94
2010	26.83
2011	28.8
2012	30.78
2013	32.55
2014	34.53
2015	36.77
2016	38.99