Year	Number of
1990	0.42
1991	0.44
1992	0.46
1993	0.47
1994	0.49
1995	0.51
1996	0.53
1997	0.55
1998	0.58
1999	0.6
2000	0.63
2001	0.65
2002	0.68
2003	0.71
2004	0.74
2005	0.78
2006	0.81
2007	0.83
2008	0.86
2009	0.88
2010	0.91
2011	0.94
2012	0.96
2013	0.99
2014	1.01
2015	1.04
2016	1.1