Year	Number of
1990	113.86
1991	115.7
1992	117.5
1993	119.12
1994	120.68
1995	122.46
1996	121.82
1997	121.44
1998	121.18
1999	120.86
2000	120.64
2001	120.67
2002	120.73
2003	120.93
2004	121.26
2005	121.76
2006	124.79
2007	127.86
2008	131.26
2009	134.82
2010	138.72
2011	140.56
2012	142.75
2013	145.06
2014	147.68
2015	150.3
2016	153.05