Year	Number of
1990	6.42
1991	6.58
1992	6.71
1993	6.8
1994	6.91
1995	7.04
1996	7.07
1997	7.09
1998	7.01
1999	7.18
2000	7.16
2001	7.23
2002	7.24
2003	7.27
2004	7.34
2005	7.29
2006	7.22
2007	7.24
2008	7.24
2009	7.25
2010	7.28
2011	7.32
2012	7.3
2013	7.28
2014	7.26
2015	7.24
2016	7.27