Year	Number of
1990	57.16
1991	56.95
1992	56.85
1993	56.79
1994	56.87
1995	57.11
1996	56.96
1997	56.9
1998	56.91
1999	56.88
2000	56.85
2001	56.32
2002	55.86
2003	55.47
2004	55.12
2005	54.84
2006	54.49
2007	54.17
2008	53.94
2009	53.85
2010	53.93
2011	55.24
2012	56.76
2013	58.33
2014	59.98
2015	61.66
2016	63.34