Year	Number of
1990	8.98
1991	9.19
1992	9.39
1993	9.62
1994	9.83
1995	10.04
1996	10.38
1997	10.76
1998	11.18
1999	11.65
2000	12.17
2001	12.51
2002	12.92
2003	13.35
2004	13.77
2005	14.14
2006	14.69
2007	15.47
2008	16.53
2009	17.83
2010	19.05
2011	20.11
2012	21.44
2013	22.93
2014	24.43
2015	25.84
2016	27.11