Year	Number of
1990	13.4
1991	13.55
1992	14.08
1993	14.7
1994	14.5
1995	13.97
1996	14.76
1997	14.04
1998	14.56
1999	15.11
2000	16.05
2001	14.75
2002	14.65
2003	14.56
2004	13.9
2005	13.6
2006	13.96
2007	13.44
2008	13.41
2009	13.53
2010	13.38
2011	13.06
2012	13.3
2013	13.32
2014	13.62
2015	13.11
2016	13.86