Year	Number of
1990	12.4
1991	12.38
1992	12.36
1993	12.19
1994	12.03
1995	11.88
1996	11.75
1997	11.64
1998	11.55
1999	11.5
2000	11.44
2001	11.32
2002	11.08
2003	10.68
2004	10.33
2005	10.11
2006	9.93
2007	9.73
2008	9.58
2009	9.59
2010	9.58
2011	10.33
2012	10.41
2013	10.71
2014	11.11
2015	11.61
2016	12.18