Year	Number of
1990	168.94
1991	169.45
1992	169.97
1993	170.35
1994	170.68
1995	170.54
1996	169.28
1997	167.85
1998	165.28
1999	163.87
2000	161.23
2001	160.86
2002	156.25
2003	153.08
2004	150.87
2005	150.69
2006	148.97
2007	147.31
2008	147.12
2009	145.94
2010	145.16
2011	142.82
2012	142.69
2013	142.71
2014	142.41
2015	142.36
2016	142.82