Year	Number of
1990	100.44
1991	105.43
1992	111.04
1993	117.25
1994	124.04
1995	131.42
1996	132.77
1997	134.37
1998	136.11
1999	138.14
2000	140.49
2001	141
2002	141.82
2003	142.91
2004	144.29
2005	145.98
2006	148.45
2007	151.17
2008	154.19
2009	157.45
2010	160.99
2011	164.64
2012	168.6
2013	172.65
2014	177.07
2015	181.9
2016	187.56