Year	Number of
1990	34.38
1991	35.08
1992	35.03
1993	35.49
1994	35.63
1995	34.96
1996	34.78
1997	34.25
1998	33.43
1999	32.4
2000	32.87
2001	30.66
2002	29.82
2003	28.81
2004	28.45
2005	28.51
2006	29.13
2007	28.56
2008	29.02
2009	29.28
2010	29.9
2011	29.8
2012	30.37
2013	31.38
2014	32.98
2015	34.56
2016	36.11