Year	Number of
1990	151.55
1991	147.27
1992	149.04
1993	151.72
1994	150.17
1995	150.29
1996	151.01
1997	151.24
1998	155.57
1999	160.4
2000	163.01
2001	167.44
2002	175.01
2003	185.03
2004	189.93
2005	190.56
2006	192.07
2007	198.27
2008	207.54
2009	215.27
2010	224.61
2011	229.46
2012	232.55
2013	235.54
2014	240.68
2015	247.33
2016	253.82