Year	Number of
1990	2.03
1991	2.01
1992	1.98
1993	1.94
1994	1.93
1995	2
1996	2.16
1997	2.34
1998	2.33
1999	2.28
2000	2.17
2001	2.12
2002	2.15
2003	2.14
2004	2.17
2005	2.28
2006	2.19
2007	2.12
2008	2.17
2009	2.21
2010	2.09
2011	1.9
2012	1.74
2013	1.66
2014	1.65
2015	1.7
2016	1.77