Year	Number of
1990	1.03
1991	1.05
1992	1.08
1993	1.07
1994	1.08
1995	1.1
1996	1.11
1997	1.13
1998	1.17
1999	1.17
2000	1.2
2001	1.23
2002	1.26
2003	1.28
2004	1.33
2005	1.35
2006	1.35
2007	1.37
2008	1.41
2009	1.45
2010	1.48
2011	1.49
2012	1.53
2013	1.58
2014	1.66
2015	1.73
2016	1.8