Year	Number of
1990	13.5
1991	13.51
1992	13.5
1993	13.08
1994	13.58
1995	13.56
1996	12.99
1997	13.02
1998	12.93
1999	12.77
2000	12.87
2001	12.7
2002	13.4
2003	14.1
2004	14.87
2005	15.41
2006	15.54
2007	15.71
2008	16.31
2009	16.13
2010	16.1
2011	16.13
2012	15.5
2013	15.42
2014	16.27
2015	16.48
2016	16.68