Year	Number of
1990	1.68
1991	1.68
1992	1.71
1993	1.7
1994	1.75
1995	1.78
1996	1.74
1997	1.63
1998	1.63
1999	1.59
2000	1.61
2001	1.53
2002	1.57
2003	1.55
2004	1.54
2005	1.53
2006	1.54
2007	1.51
2008	1.52
2009	1.53
2010	1.61
2011	1.66
2012	1.7
2013	1.74
2014	1.9
2015	1.93
2016	1.99