Year	Number of
1990	170.42
1991	170.36
1992	170.53
1993	168.95
1994	167.3
1995	166.1
1996	159.63
1997	154.9
1998	152.08
1999	149.24
2000	149.76
2001	152.23
2002	156.9
2003	162.59
2004	166.45
2005	169.33
2006	171.3
2007	172.18
2008	171.49
2009	170.57
2010	170.38
2011	170.31
2012	170.12
2013	170.62
2014	172.43
2015	170.21
2016	167.6