Year	Number of
1990	104.08
1991	104.5
1992	105.71
1993	104.85
1994	105.68
1995	108.04
1996	113.21
1997	119.62
1998	127.32
1999	133.69
2000	138.45
2001	142.59
2002	145.73
2003	150.34
2004	155.54
2005	161.61
2006	168.74
2007	176.09
2008	183.3
2009	191.41
2010	198.71
2011	205.08
2012	212.56
2013	218.68
2014	221.54
2015	224.82
2016	230.21