Year	Number of
1990	14.87
1991	15.25
1992	15.56
1993	16.31
1994	16.58
1995	16.77
1996	16.63
1997	15.95
1998	15.79
1999	14.97
2000	15.24
2001	13.8
2002	13.82
2003	13.78
2004	13.78
2005	14.02
2006	13.99
2007	13.71
2008	13.77
2009	13.82
2010	14.16
2011	14.11
2012	14.58
2013	15.08
2014	15.53
2015	16.01
2016	16.4