Year	Number of
1990	8.79
1991	8.93
1992	9.06
1993	9.26
1994	9.56
1995	10.03
1996	10.25
1997	10.82
1998	11.29
1999	12.12
2000	12.94
2001	13.14
2002	13.24
2003	13.58
2004	13.5
2005	13.24
2006	13.09
2007	12.68
2008	12.62
2009	12.85
2010	12.26
2011	11.95
2012	11.96
2013	11.96
2014	12.04
2015	12.17
2016	12.28