Year	Number of
1990	129.47
1991	131.36
1992	130.66
1993	129.72
1994	130.01
1995	129.37
1996	130.67
1997	131.41
1998	132.24
1999	133.07
2000	134.64
2001	135.32
2002	135.1
2003	135.93
2004	136.89
2005	137.53
2006	138.81
2007	139.59
2008	138.85
2009	139.48
2010	139.88
2011	139.23
2012	139.81
2013	139.83
2014	139.58
2015	139.24
2016	139.02