Year	Number of
1990	107.94
1991	107.7
1992	107.16
1993	106.63
1994	106.48
1995	106.94
1996	108.25
1997	110.41
1998	113.38
1999	116.59
2000	119.92
2001	122.85
2002	126
2003	129.28
2004	132.63
2005	136.08
2006	139.4
2007	142.6
2008	145.81
2009	149.23
2010	153.01
2011	156.71
2012	160.85
2013	165.11
2014	169.64
2015	174.46
2016	180.75