Year	Number of
1990	111.06
1991	109.47
1992	106.57
1993	103.48
1994	101.97
1995	102.93
1996	106.44
1997	112.15
1998	121.53
1999	129.74
2000	135.82
2001	133.82
2002	131.01
2003	126.32
2004	122.82
2005	120.85
2006	124.89
2007	129.54
2008	134.3
2009	138.71
2010	142.85
2011	147.9
2012	153.18
2013	159.88
2014	167.49
2015	176.16
2016	184.68