Year	Number of
1990	56.82
1991	59.39
1992	62.11
1993	64.81
1994	67.87
1995	70.93
1996	73.68
1997	77.74
1998	81.99
1999	87.09
2000	91.7
2001	97.22
2002	101.41
2003	105.76
2004	109.03
2005	111.53
2006	115.5
2007	118.65
2008	122.79
2009	128.67
2010	135.56
2011	141.23
2012	146.82
2013	152.88
2014	157.8
2015	162.6
2016	167.06