Year	Number of
1990	1
1991	1.01
1992	1.03
1993	1.05
1994	1.07
1995	1.1
1996	1.12
1997	1.14
1998	1.17
1999	1.2
2000	1.24
2001	1.27
2002	1.29
2003	1.33
2004	1.37
2005	1.41
2006	1.46
2007	1.51
2008	1.57
2009	1.63
2010	1.69
2011	1.74
2012	1.79
2013	1.85
2014	1.91
2015	1.98
2016	2.04