Year	Number of
1990	141.85
1991	137.94
1992	136.5
1993	135.68
1994	135.46
1995	134.79
1996	132.21
1997	128.95
1998	125.77
1999	124.15
2000	124.6
2001	124.97
2002	126.53
2003	127.5
2004	129.85
2005	132.79
2006	134.83
2007	139.15
2008	142.59
2009	147.48
2010	152.43
2011	155.06
2012	158.61
2013	162.04
2014	165.56
2015	169.65
2016	174.42