Year	Number of
1990	116.05
1991	116.78
1992	116.72
1993	116.11
1994	115.49
1995	115.26
1996	114.51
1997	114.33
1998	114.91
1999	116.46
2000	119.14
2001	121.45
2002	125.18
2003	129.71
2004	134.23
2005	138.49
2006	141.35
2007	143.4
2008	145.21
2009	147.02
2010	149.23
2011	151.08
2012	153.24
2013	155.5
2014	157.84
2015	160.25
2016	163.1