Year	Number of
1990	1.58
1991	1.63
1992	1.67
1993	1.72
1994	1.77
1995	1.82
1996	1.83
1997	1.85
1998	1.86
1999	1.89
2000	1.9
2001	1.93
2002	1.99
2003	2.01
2004	2.04
2005	2.13
2006	2.15
2007	2.15
2008	2.13
2009	2.16
2010	2.19
2011	2.15
2012	2.13
2013	2.13
2014	2.2
2015	2.23
2016	2.22