Year	Number of
1990	0.54
1991	0.57
1992	0.59
1993	0.62
1994	0.65
1995	0.69
1996	0.72
1997	0.75
1998	0.79
1999	0.83
2000	0.87
2001	0.91
2002	0.95
2003	1
2004	1.05
2005	1.11
2006	1.16
2007	1.19
2008	1.22
2009	1.25
2010	1.28
2011	1.3
2012	1.33
2013	1.35
2014	1.38
2015	1.41
2016	1.45