Year	Number of
1990	6.48
1991	6.9
1992	7.21
1993	7.25
1994	7.25
1995	7.51
1996	7.29
1997	7.63
1998	7.6
1999	7.6
2000	7.83
2001	7.67
2002	7.6
2003	7.42
2004	7.25
2005	7.2
2006	7.2
2007	7.13
2008	7.13
2009	7.15
2010	7.16
2011	6.99
2012	6.79
2013	6.57
2014	6.39
2015	6.24
2016	6.46