Year	Number of
1990	1.3
1991	1.36
1992	1.41
1993	1.45
1994	1.49
1995	1.53
1996	1.55
1997	1.57
1998	1.58
1999	1.63
2000	1.65
2001	1.69
2002	1.72
2003	1.75
2004	1.79
2005	1.8
2006	1.81
2007	1.83
2008	1.85
2009	1.87
2010	1.91
2011	1.95
2012	1.97
2013	2
2014	2.02
2015	2.05
2016	2.08