Year	Number of
1990	7.03
1991	6.93
1992	6.83
1993	6.76
1994	6.72
1995	6.66
1996	6.7
1997	6.68
1998	6.92
1999	6.72
2000	6.85
2001	6.43
2002	6.35
2003	6.23
2004	6.08
2005	5.96
2006	5.85
2007	5.68
2008	5.65
2009	5.68
2010	5.76
2011	5.84
2012	6.02
2013	6.27
2014	6.68
2015	6.86
2016	7