Year	Number of
1990	12.02
1991	12.14
1992	11.94
1993	11.31
1994	10.73
1995	10.72
1996	10.22
1997	10.07
1998	10.75
1999	11.7
2000	13.66
2001	14.68
2002	16.12
2003	16.25
2004	16.57
2005	17.03
2006	16.59
2007	16.09
2008	15.54
2009	15.18
2010	14.75
2011	14.09
2012	13.84
2013	13.73
2014	13.54
2015	13.27
2016	13.27