Year	Number of
1990	153.51
1991	152.16
1992	150.84
1993	149.53
1994	149.25
1995	149.92
1996	152
1997	155.19
1998	159.2
1999	161.4
2000	163.59
2001	164.08
2002	165.04
2003	166.08
2004	167.18
2005	168.46
2006	169.75
2007	170.78
2008	171.98
2009	173.47
2010	175.37
2011	176.76
2012	178.35
2013	180.04
2014	182.31
2015	185.09
2016	189.13