Year	Number of
1990	1.07
1991	1.1
1992	1.12
1993	1.14
1994	1.15
1995	1.16
1996	1.17
1997	1.18
1998	1.18
1999	1.18
2000	1.19
2001	1.22
2002	1.26
2003	1.3
2004	1.34
2005	1.38
2006	1.44
2007	1.49
2008	1.53
2009	1.56
2010	1.6
2011	1.66
2012	1.74
2013	1.82
2014	1.9
2015	1.97
2016	2.07