Year	Number of
1990	100.32
1991	102.12
1992	103.57
1993	104.77
1994	105.3
1995	110.46
1996	115.06
1997	119.99
1998	125.96
1999	130.49
2000	133.18
2001	136.09
2002	139.75
2003	143.25
2004	147.39
2005	148.21
2006	147.57
2007	146.21
2008	145.67
2009	146
2010	145.14
2011	142.74
2012	141.77
2013	142.23
2014	143.04
2015	143.96
2016	144.69