Year	Number of
1990	4.79
1991	4.78
1992	4.75
1993	4.72
1994	4.74
1995	4.93
1996	5.34
1997	5.6
1998	5.56
1999	5.44
2000	5.44
2001	5.47
2002	5.38
2003	5.41
2004	5.52
2005	5.55
2006	5.39
2007	5.25
2008	5.28
2009	5.46
2010	5.32
2011	5
2012	4.66
2013	4.51
2014	4.63
2015	4.83
2016	5.08