Year	Number of
1990	5.98
1991	6.5
1992	7.08
1993	7.72
1994	8.47
1995	9.38
1996	10.02
1997	10.79
1998	11.61
1999	12.52
2000	13.5
2001	14.02
2002	14.57
2003	15.2
2004	15.9
2005	16.69
2006	17.76
2007	18.89
2008	20.15
2009	21.46
2010	22.83
2011	23.96
2012	25.16
2013	26.36
2014	27.67
2015	29.11
2016	30.56