Year	Number of
1990	10.58
1991	10.84
1992	11.11
1993	11.39
1994	11.73
1995	12.11
1996	12.12
1997	11.96
1998	11.9
1999	11.97
2000	12.1
2001	12.13
2002	12.06
2003	11.95
2004	11.8
2005	11.82
2006	11.88
2007	11.88
2008	12.12
2009	12.54
2010	12.99
2011	13.63
2012	14.13
2013	14.62
2014	15.25
2015	16.16
2016	17.19