Year	Number of
1990	3.2
1991	2.74
1992	2.9
1993	3.16
1994	3.13
1995	2.56
1996	2.91
1997	3.14
1998	2.95
1999	2.82
2000	2.79
2001	2.66
2002	2.29
2003	2.08
2004	2.08
2005	1.86
2006	1.65
2007	1.95
2008	1.86
2009	1.91
2010	2.08
2011	2.06
2012	2.05
2013	2.17
2014	2.12
2015	2.2
2016	2.16