Year	Number of
1990	19
1991	17.98
1992	17.17
1993	17.63
1994	15.27
1995	14.81
1996	15.26
1997	15.88
1998	16.67
1999	15.34
2000	16.26
2001	16.91
2002	16.4
2003	17.66
2004	17.84
2005	20.42
2006	22.19
2007	24.28
2008	26.61
2009	27.56
2010	29.07
2011	28.02
2012	28.47
2013	28.66
2014	30.42
2015	32.92
2016	35.4