Year	Number of
1990	110.91
1991	112.15
1992	113.86
1993	115.83
1994	117.94
1995	120.29
1996	120.93
1997	121.66
1998	122.33
1999	123.02
2000	123.93
2001	123.7
2002	123.68
2003	123.75
2004	123.91
2005	124.37
2006	125.93
2007	127.55
2008	129.59
2009	131.85
2010	134.44
2011	136.2
2012	138.22
2013	140.29
2014	142.6
2015	145.19
2016	148.18