Year	Number of
1990	0.68
1991	0.69
1992	0.71
1993	0.73
1994	0.76
1995	0.78
1996	0.8
1997	0.81
1998	0.83
1999	0.86
2000	0.88
2001	0.89
2002	0.9
2003	0.92
2004	0.94
2005	0.95
2006	0.96
2007	0.97
2008	0.99
2009	1
2010	1.01
2011	1.03
2012	1.05
2013	1.06
2014	1.08
2015	1.11
2016	1.14