Year	Number of
1990	118.85
1991	119.24
1992	119.17
1993	117.81
1994	118.09
1995	119.03
1996	119.54
1997	122.99
1998	121.87
1999	120.24
2000	118.85
2001	120.55
2002	125.81
2003	128.98
2004	133.35
2005	137.29
2006	140.36
2007	144.65
2008	147.03
2009	150.23
2010	153.95
2011	157.57
2012	161.27
2013	164.28
2014	168.02
2015	172.75
2016	178.38