Year	Number of
1990	18.75
1991	17.49
1992	16.61
1993	17.2
1994	15.21
1995	15.03
1996	15.52
1997	16.12
1998	16.92
1999	15.46
2000	16.32
2001	17.07
2002	16.56
2003	17.83
2004	18.01
2005	20.67
2006	22.5
2007	24.67
2008	27.01
2009	28.03
2010	29.24
2011	27.91
2012	28.14
2013	28.2
2014	29.98
2015	32.22
2016	34.75