Year	Number of
1990	3.33
1991	3.28
1992	3.2
1993	3.12
1994	3.07
1995	3.16
1996	3.41
1997	3.55
1998	3.45
1999	3.36
2000	3.3
2001	3.29
2002	3.22
2003	3.15
2004	3.16
2005	3.17
2006	3.01
2007	2.93
2008	2.95
2009	3
2010	2.88
2011	2.67
2012	2.44
2013	2.33
2014	2.33
2015	2.39
2016	2.48