Year	Number of
1990	26.44
1991	27.28
1992	28.34
1993	29.44
1994	30.59
1995	31.87
1996	32.13
1997	32.44
1998	32.79
1999	33.21
2000	33.72
2001	33.32
2002	32.98
2003	32.68
2004	32.41
2005	32.15
2006	32.03
2007	31.9
2008	31.78
2009	31.67
2010	31.58
2011	31.38
2012	31.21
2013	31.04
2014	30.88
2015	30.71
2016	31.94