Year	Number of
1990	9.57
1991	9.86
1992	10.14
1993	10.39
1994	10.64
1995	10.89
1996	11.22
1997	11.58
1998	11.97
1999	12.43
2000	12.9
2001	13.18
2002	13.5
2003	13.85
2004	14.14
2005	14.35
2006	14.81
2007	15.55
2008	16.49
2009	17.82
2010	18.86
2011	19.71
2012	20.86
2013	22.21
2014	23.62
2015	25.04
2016	26.37