Year	Number of
1990	60.16
1991	59.32
1992	59.65
1993	59.19
1994	58.84
1995	58.2
1996	58.78
1997	58.97
1998	57.65
1999	56.63
2000	55.82
2001	55.72
2002	55.8
2003	55.44
2004	54.58
2005	54.17
2006	53.93
2007	53.94
2008	53.8
2009	54.04
2010	55.19
2011	55.74
2012	55.14
2013	55.16
2014	58.44
2015	60.1
2016	61.29