Year	Number of
1990	1.08
1991	1.12
1992	1.17
1993	1.22
1994	1.26
1995	1.3
1996	1.35
1997	1.37
1998	1.51
1999	1.56
2000	1.54
2001	1.5
2002	1.51
2003	1.55
2004	1.6
2005	1.66
2006	1.72
2007	1.75
2008	1.78
2009	1.84
2010	1.86
2011	2.06
2012	2.18
2013	2.24
2014	2.3
2015	2.36
2016	2.4