Year	Number of
1990	0.63
1991	0.65
1992	0.68
1993	0.71
1994	0.75
1995	0.79
1996	0.81
1997	0.84
1998	0.9
1999	0.85
2000	0.81
2001	0.78
2002	0.82
2003	0.85
2004	0.88
2005	0.92
2006	0.97
2007	1
2008	1.03
2009	1.05
2010	1.05
2011	1.11
2012	1.15
2013	1.21
2014	1.26
2015	1.31
2016	1.35