Year	Number of
1990	2.07
1991	2.13
1992	2.2
1993	2.19
1994	2.24
1995	2.26
1996	2.15
1997	1.99
1998	1.96
1999	1.89
2000	1.85
2001	1.75
2002	1.8
2003	1.78
2004	1.77
2005	1.77
2006	1.81
2007	1.78
2008	1.8
2009	1.84
2010	1.88
2011	1.99
2012	2.07
2013	2.17
2014	2.31
2015	2.31
2016	2.4