Year	Number of
1990	4.23
1991	4.34
1992	4.43
1993	4.52
1994	4.6
1995	4.66
1996	4.67
1997	4.67
1998	4.67
1999	4.68
2000	4.69
2001	4.71
2002	4.78
2003	4.79
2004	4.78
2005	4.9
2006	4.91
2007	4.85
2008	4.78
2009	4.83
2010	4.88
2011	4.77
2012	4.72
2013	4.71
2014	4.86
2015	4.88
2016	4.76