Year	Number of
1990	111.96
1991	114.12
1992	115.72
1993	117.17
1994	119.1
1995	120.07
1996	119.98
1997	119.87
1998	119.34
1999	117.99
2000	117.33
2001	117.96
2002	119.16
2003	121.66
2004	124.11
2005	126.25
2006	129.54
2007	132.3
2008	135.55
2009	139.64
2010	144.86
2011	150.94
2012	156.08
2013	161.53
2014	168.12
2015	175.13
2016	181.13