Year	Number of
1990	3.78
1991	3.91
1992	4.07
1993	4.25
1994	4.43
1995	4.59
1996	4.84
1997	5.01
1998	5.1
1999	5.16
2000	5.29
2001	5.25
2002	5.26
2003	5.21
2004	5.26
2005	5.16
2006	5.13
2007	5.08
2008	4.96
2009	4.96
2010	4.97
2011	4.91
2012	4.96
2013	4.88
2014	4.86
2015	4.86
2016	4.88