Year	Number of
1990	1.03
1991	1.07
1992	1.12
1993	1.17
1994	1.23
1995	1.28
1996	1.34
1997	1.39
1998	1.5
1999	1.57
2000	1.68
2001	1.71
2002	1.75
2003	1.82
2004	1.92
2005	2
2006	2.1
2007	2.18
2008	2.23
2009	2.31
2010	2.4
2011	2.51
2012	2.61
2013	2.71
2014	2.82
2015	2.94
2016	3.06