Year	Number of
1990	53.87
1991	54.66
1992	56
1993	56.32
1994	55.66
1995	55.99
1996	56.29
1997	56.42
1998	55.72
1999	55.23
2000	54.88
2001	53.84
2002	52.92
2003	53.05
2004	52.34
2005	52.88
2006	52.72
2007	53.62
2008	53.48
2009	54.79
2010	55.28
2011	56.71
2012	57.13
2013	58.73
2014	62.76
2015	65.61
2016	68.15