Year	Number of
1990	8.47
1991	8.42
1992	8.74
1993	9.01
1994	9.02
1995	8.82
1996	8.7
1997	8.75
1998	9.01
1999	9.44
2000	9.8
2001	10.06
2002	10.34
2003	10.38
2004	10.32
2005	10.15
2006	10.12
2007	10.02
2008	9.94
2009	9.94
2010	10.05
2011	10.11
2012	10.29
2013	10.54
2014	10.94
2015	11.24
2016	11.49