Year	Number of
1990	0.95
1991	0.98
1992	1.01
1993	1.04
1994	1.06
1995	1.09
1996	1.13
1997	1.17
1998	1.22
1999	1.26
2000	1.31
2001	1.38
2002	1.45
2003	1.53
2004	1.62
2005	1.71
2006	1.79
2007	1.88
2008	1.97
2009	2.06
2010	2.16
2011	2.27
2012	2.38
2013	2.49
2014	2.61
2015	2.74
2016	2.95