Year	Number of
1990	10.81
1991	10.84
1992	10.62
1993	10.09
1994	9.64
1995	9.62
1996	9.32
1997	9.31
1998	9.97
1999	10.88
2000	12.61
2001	13.63
2002	15
2003	15.36
2004	15.85
2005	16.41
2006	16.11
2007	15.71
2008	15.25
2009	14.96
2010	14.61
2011	13.94
2012	13.65
2013	13.49
2014	13.25
2015	12.96
2016	12.93