Year	Number of
1990	4.87
1991	4.82
1992	4.86
1993	4.76
1994	4.88
1995	4.79
1996	4.77
1997	4.72
1998	4.65
1999	4.53
2000	4.53
2001	4.55
2002	4.66
2003	4.64
2004	4.55
2005	4.35
2006	4.2
2007	3.93
2008	3.87
2009	3.82
2010	3.8
2011	3.79
2012	3.85
2013	3.83
2014	3.9
2015	3.87
2016	3.83