Year	Number of
1990	6.99
1991	7.4
1992	8.03
1993	8.91
1994	9.7
1995	10.75
1996	11.31
1997	12.04
1998	12.7
1999	13.33
2000	13.9
2001	14.63
2002	14.72
2003	14.81
2004	14.78
2005	15.18
2006	15.56
2007	15.79
2008	16.44
2009	17.21
2010	17.56
2011	18.11
2012	18.8
2013	19.6
2014	20.59
2015	21.48
2016	22.41