Year	Number of
1990	79.85
1991	77.16
1992	77.91
1993	76.32
1994	78.25
1995	76.55
1996	82.5
1997	87.42
1998	84.73
1999	93.36
2000	98.03
2001	102.52
2002	108.69
2003	112.22
2004	120
2005	124.14
2006	131.69
2007	136.83
2008	142.95
2009	153.95
2010	160.31
2011	167.73
2012	174.99
2013	177.98
2014	178.29
2015	171.49
2016	167.86