Year	Number of
1990	42.2
1991	41.56
1992	40.94
1993	40.63
1994	39.87
1995	39.08
1996	37.95
1997	38.11
1998	36.82
1999	35.21
2000	33.83
2001	34.21
2002	34.06
2003	34.28
2004	32.96
2005	31.8
2006	31.13
2007	30.9
2008	30.48
2009	30.42
2010	31.06
2011	32.19
2012	32.49
2013	32.68
2014	34.1
2015	34.96
2016	35.66