Year	Number of
1990	10.84
1991	11.45
1992	11.99
1993	12.5
1994	12.48
1995	12.5
1996	12.54
1997	12.77
1998	12.73
1999	12.64
2000	13.05
2001	12.78
2002	12.81
2003	12.34
2004	12.1
2005	11.86
2006	11.41
2007	11.24
2008	11.05
2009	11.02
2010	10.85
2011	10.4
2012	10.09
2013	9.85
2014	9.72
2015	9.56
2016	9.9