Year	Number of
1990	13.52
1991	13.12
1992	12.21
1993	11.02
1994	10.56
1995	10.21
1996	9.93
1997	9.73
1998	10.98
1999	11.58
2000	10.78
2001	10.79
2002	10.72
2003	10.66
2004	10.57
2005	10.52
2006	10.53
2007	10.48
2008	11.08
2009	10.37
2010	10.28
2011	10.5
2012	10.76
2013	11.05
2014	11.68
2015	11.64
2016	11.78