Year	Number of
1990	151.91
1991	155.72
1992	159.15
1993	161.3
1994	163.37
1995	166.72
1996	169.75
1997	174
1998	178.54
1999	182.96
2000	188.03
2001	193.69
2002	200.17
2003	206.95
2004	213.91
2005	220.72
2006	227.13
2007	232.17
2008	236.13
2009	240.85
2010	245.59
2011	249.59
2012	253.12
2013	256.4
2014	259.48
2015	262.7
2016	267.43