Year	Number of
1990	1.2
1991	1.23
1992	1.27
1993	1.29
1994	1.32
1995	1.34
1996	1.43
1997	1.53
1998	1.65
1999	1.77
2000	1.9
2001	1.97
2002	2.02
2003	2.08
2004	2.16
2005	2.2
2006	2.26
2007	2.32
2008	2.38
2009	2.43
2010	2.47
2011	2.52
2012	2.62
2013	2.7
2014	2.78
2015	2.86
2016	2.95