Year	Number of
1990	0.54
1991	0.56
1992	0.58
1993	0.6
1994	0.62
1995	0.64
1996	0.66
1997	0.68
1998	0.7
1999	0.72
2000	0.75
2001	0.78
2002	0.82
2003	0.86
2004	0.9
2005	0.95
2006	0.99
2007	1.02
2008	1.05
2009	1.08
2010	1.11
2011	1.14
2012	1.17
2013	1.2
2014	1.23
2015	1.26
2016	1.3