Year	Number of
1990	170.97
1991	176.54
1992	181.95
1993	187.24
1994	192.85
1995	200.53
1996	208.7
1997	218.86
1998	231.61
1999	247.89
2000	281.03
2001	299.89
2002	321.75
2003	346.77
2004	374.21
2005	404.53
2006	418.06
2007	430.43
2008	442.86
2009	456.24
2010	471.56
2011	475.5
2012	481.42
2013	488.56
2014	496.07
2015	503.31
2016	508.55