Year	Number of
1990	0.3
1991	0.32
1992	0.34
1993	0.37
1994	0.4
1995	0.42
1996	0.44
1997	0.46
1998	0.47
1999	0.49
2000	0.51
2001	0.55
2002	0.59
2003	0.63
2004	0.68
2005	0.72
2006	0.74
2007	0.76
2008	0.79
2009	0.81
2010	0.83
2011	0.86
2012	0.89
2013	0.93
2014	0.96
2015	1
2016	1.04