Year	Number of
1990	177.9
1991	175.34
1992	178.47
1993	178.58
1994	176.05
1995	179.12
1996	179.57
1997	178.99
1998	174.59
1999	171.74
2000	168.67
2001	163.6
2002	162.64
2003	163.13
2004	159.78
2005	159.21
2006	158.48
2007	157.3
2008	154.07
2009	156.98
2010	157.55
2011	158.19
2012	156.22
2013	157.4
2014	166.36
2015	165.69
2016	166.2