Year	Number of
1990	0.56
1991	0.58
1992	0.6
1993	0.63
1994	0.65
1995	0.68
1996	0.7
1997	0.72
1998	0.75
1999	0.78
2000	0.8
2001	0.84
2002	0.88
2003	0.92
2004	0.96
2005	1.01
2006	1.06
2007	1.08
2008	1.1
2009	1.13
2010	1.15
2011	1.16
2012	1.18
2013	1.2
2014	1.21
2015	1.23
2016	1.26