Year	Number of
1990	14.87
1991	16.25
1992	17.73
1993	19.27
1994	20.8
1995	21.82
1996	23.91
1997	24.55
1998	24.93
1999	26.87
2000	28.31
2001	28.27
2002	28.53
2003	28.26
2004	27.32
2005	27.46
2006	27.55
2007	27.36
2008	27.56
2009	28.35
2010	29.05
2011	29.44
2012	28.89
2013	30.5
2014	32.04
2015	34.22
2016	34.83