Year	Number of
1990	11.04
1991	10.86
1992	10.6
1993	10.28
1994	9.99
1995	9.76
1996	9.47
1997	9.6
1998	9.61
1999	9.54
2000	9.68
2001	9.6
2002	9.43
2003	9.41
2004	9.45
2005	9.57
2006	9.47
2007	9.4
2008	9.36
2009	9.37
2010	9.49
2011	9.58
2012	9.75
2013	9.95
2014	10.14
2015	10.33
2016	10.52