Year	Number of
1990	58.6
1991	60.55
1992	62.78
1993	65.23
1994	67.91
1995	70.83
1996	74.65
1997	78.76
1998	83.2
1999	87.94
2000	93.08
2001	94.86
2002	96.81
2003	99.24
2004	101.82
2005	104.68
2006	109.52
2007	114.77
2008	120.19
2009	126.2
2010	133.17
2011	138.22
2012	143.78
2013	149.37
2014	154.33
2015	158.47
2016	163.35