Year	Number of
1990	1.02
1991	1.05
1992	1.06
1993	1.09
1994	1.11
1995	1.14
1996	1.16
1997	1.19
1998	1.23
1999	1.28
2000	1.31
2001	1.34
2002	1.38
2003	1.42
2004	1.48
2005	1.52
2006	1.57
2007	1.62
2008	1.66
2009	1.7
2010	1.75
2011	1.8
2012	1.86
2013	1.92
2014	1.98
2015	2.04
2016	2.11