Year	Number of
1990	9.74
1991	10.27
1992	10.78
1993	11.41
1994	12.16
1995	13.01
1996	13.88
1997	14.8
1998	15.38
1999	15.94
2000	16.65
2001	17.04
2002	17.53
2003	17.86
2004	18.31
2005	18.95
2006	19.46
2007	19.9
2008	20.41
2009	21.11
2010	21.76
2011	22.33
2012	22.88
2013	23.38
2014	24
2015	24.68
2016	25.56