Year	Number of
1990	1.81
1991	1.82
1992	1.83
1993	1.84
1994	1.86
1995	1.95
1996	1.88
1997	1.75
1998	1.77
1999	1.75
2000	1.79
2001	1.69
2002	1.73
2003	1.71
2004	1.72
2005	1.73
2006	1.72
2007	1.67
2008	1.69
2009	1.69
2010	1.71
2011	1.78
2012	1.87
2013	1.95
2014	2.08
2015	2.15
2016	2.17