Year	Number of
1990	164.92
1991	165.67
1992	166.18
1993	166.49
1994	166.89
1995	166.93
1996	166.7
1997	166.44
1998	166.77
1999	166.02
2000	166.46
2001	167.91
2002	165.53
2003	165.92
2004	165.96
2005	166.88
2006	167.48
2007	167.37
2008	167.79
2009	167.89
2010	167.94
2011	166.52
2012	167.27
2013	168.19
2014	168.75
2015	169.68
2016	171.67