Year	Number of
1990	8.3
1991	8.27
1992	8.34
1993	8.38
1994	8.84
1995	8.81
1996	8.57
1997	8.8
1998	9.19
1999	9.32
2000	9.65
2001	9.85
2002	10.23
2003	10.19
2004	9.95
2005	10
2006	9.81
2007	9.4
2008	9.8
2009	10.01
2010	10.58
2011	11.07
2012	11.72
2013	12.24
2014	12.88
2015	13.4
2016	14.16