Year	Number of
1990	103.39
1991	104.17
1992	105.42
1993	106.61
1994	108.07
1995	109.51
1996	110.45
1997	108.97
1998	107.82
1999	106.15
2000	105.57
2001	104.39
2002	104.95
2003	106.84
2004	110.01
2005	113.03
2006	115.85
2007	118.2
2008	121.52
2009	125.32
2010	130.9
2011	136.09
2012	141.12
2013	145.89
2014	151.25
2015	156.48
2016	161.81