Year	Number of
1990	118.13
1991	118.26
1992	118.53
1993	118.79
1994	119.15
1995	119.86
1996	119.81
1997	120.06
1998	120.42
1999	120.91
2000	121.72
2001	123.06
2002	124.71
2003	126.53
2004	128.51
2005	130.84
2006	133.59
2007	136.25
2008	139.55
2009	143.01
2010	146.91
2011	150.19
2012	153.84
2013	157.84
2014	161.96
2015	166.18
2016	170.83