Year	Number of
1990	0.55
1991	0.56
1992	0.57
1993	0.58
1994	0.58
1995	0.58
1996	0.63
1997	0.68
1998	0.73
1999	0.79
2000	0.86
2001	0.88
2002	0.9
2003	0.92
2004	0.94
2005	0.96
2006	0.96
2007	0.97
2008	0.98
2009	0.99
2010	0.99
2011	0.99
2012	0.99
2013	1
2014	1.01
2015	1.02
2016	1.02