Year	Number of
1990	71
1991	72.51
1992	73.32
1993	73.75
1994	74.21
1995	75.09
1996	79.35
1997	84.5
1998	90.32
1999	96.68
2000	103.5
2001	110.29
2002	117.64
2003	125.54
2004	134.07
2005	143.43
2006	145.91
2007	148.44
2008	151.36
2009	154.42
2010	157.73
2011	161.15
2012	165.02
2013	169.23
2014	173.65
2015	178.24
2016	183.32