Year	Number of
1990	5.95
1991	5.74
1992	5.6
1993	5.44
1994	5.27
1995	5.19
1996	5.21
1997	5.05
1998	5.06
1999	4.8
2000	4.87
2001	4.6
2002	4.54
2003	4.49
2004	4.41
2005	4.31
2006	4.29
2007	4.1
2008	4.1
2009	4.04
2010	4.12
2011	4.2
2012	4.24
2013	4.22
2014	4.48
2015	4.53
2016	4.64