Year	Number of
1990	10.32
1991	9.29
1992	8.6
1993	8.64
1994	8.46
1995	9.18
1996	9.54
1997	9.88
1998	10.27
1999	11.22
2000	11.92
2001	11.31
2002	11.36
2003	10.59
2004	10.49
2005	11.34
2006	11.7
2007	12.83
2008	14.06
2009	14.88
2010	15.3
2011	14.98
2012	15.62
2013	15.39
2014	17.16
2015	18.78
2016	20.61