Year	Number of
1990	1.67
1991	1.7
1992	1.72
1993	1.76
1994	1.79
1995	1.82
1996	1.78
1997	1.74
1998	1.71
1999	1.68
2000	1.66
2001	1.64
2002	1.63
2003	1.61
2004	1.6
2005	1.6
2006	1.59
2007	1.59
2008	1.6
2009	1.61
2010	1.63
2011	1.68
2012	1.73
2013	1.8
2014	1.87
2015	1.95
2016	2.03