Year	Number of
1990	4.84
1991	5.18
1992	5.55
1993	5.95
1994	6.37
1995	6.82
1996	7.25
1997	7.7
1998	8.19
1999	8.71
2000	9.28
2001	9.83
2002	10.41
2003	11
2004	11.62
2005	12.25
2006	12.55
2007	12.84
2008	13.1
2009	13.34
2010	13.58
2011	13.65
2012	13.76
2013	13.92
2014	14.11
2015	14.34
2016	14.64