Year	Number of
1990	52.84
1991	52.87
1992	52.67
1993	52.88
1994	53.32
1995	53.84
1996	54.15
1997	54.42
1998	54.97
1999	55.25
2000	54.2
2001	56.96
2002	56.04
2003	55.55
2004	55.7
2005	55.38
2006	55.37
2007	54.07
2008	52.78
2009	51.61
2010	51.52
2011	51.18
2012	51.06
2013	50.9
2014	50.66
2015	50.42
2016	50.31