Year	Number of
1990	9.36
1991	9.44
1992	9.57
1993	9.73
1994	9.91
1995	10.11
1996	10.35
1997	10.6
1998	10.88
1999	11.2
2000	11.57
2001	12.03
2002	12.54
2003	13.11
2004	13.73
2005	14.41
2006	15.21
2007	16.06
2008	16.99
2009	18.01
2010	19.15
2011	20.2
2012	21.36
2013	22.61
2014	23.99
2015	25.49
2016	27.09