Year	Number of
1990	7.97
1991	8.08
1992	8.15
1993	8.06
1994	8
1995	7.96
1996	7.91
1997	7.72
1998	7.72
1999	7.27
2000	6.94
2001	6.72
2002	6.73
2003	6.6
2004	6.36
2005	6.4
2006	6.32
2007	6.3
2008	6.32
2009	6.35
2010	6.52
2011	6.64
2012	6.68
2013	6.9
2014	7
2015	7.13
2016	7.49