Year	Number of
1990	1.04
1991	1.07
1992	1.1
1993	1.12
1994	1.13
1995	1.16
1996	1.17
1997	1.22
1998	1.25
1999	1.29
2000	1.32
2001	1.37
2002	1.42
2003	1.48
2004	1.54
2005	1.6
2006	1.67
2007	1.71
2008	1.75
2009	1.79
2010	1.83
2011	1.87
2012	1.9
2013	1.94
2014	1.98
2015	2.01
2016	2.1