Year	Number of
1990	29.47
1991	29.41
1992	29.11
1993	29.68
1994	31.35
1995	31.93
1996	33.92
1997	34.42
1998	35.44
1999	36.89
2000	37.59
2001	38.99
2002	37.84
2003	38.95
2004	39.49
2005	37.64
2006	37.63
2007	35.64
2008	35.8
2009	34.99
2010	33.23
2011	33.3
2012	32.58
2013	31.58
2014	31.35
2015	31.25
2016	31.17