Year	Number of
1990	115.64
1991	115.02
1992	114.33
1993	113.5
1994	113.54
1995	114.3
1996	115.93
1997	118.59
1998	122.09
1999	124.9
2000	127.31
2001	129.44
2002	132.88
2003	136.26
2004	139.4
2005	142.78
2006	146.16
2007	149.79
2008	153.36
2009	156.31
2010	159.98
2011	162.8
2012	167.94
2013	171.2
2014	175.47
2015	180.01
2016	185.05