Year	Number of
1990	53.15
1991	56.85
1992	58.99
1993	64.22
1994	67.3
1995	70.98
1996	74.23
1997	79.23
1998	84.11
1999	87.38
2000	90.24
2001	91.85
2002	97.6
2003	103.8
2004	109.74
2005	114.83
2006	123.42
2007	129.3
2008	134.79
2009	139.73
2010	145.87
2011	152.58
2012	155.52
2013	158.41
2014	161.39
2015	164
2016	167.69