Year	Number of
1990	35.49
1991	34.83
1992	36.3
1993	35.47
1994	36.33
1995	35.07
1996	33.97
1997	32.9
1998	32.93
1999	33.39
2000	32.23
2001	30.79
2002	30.12
2003	28.04
2004	27.63
2005	26.94
2006	25.42
2007	23.22
2008	24.15
2009	23.77
2010	22.26
2011	23.36
2012	23.8
2013	24.22
2014	24.67
2015	25.12
2016	25.67