Year	Number of
1990	278.2
1991	286.93
1992	299.71
1993	311.18
1994	318.83
1995	336.29
1996	344.17
1997	353.25
1998	363.46
1999	370.25
2000	385.23
2001	400.84
2002	418.36
2003	428.18
2004	441.99
2005	457.78
2006	466.18
2007	476.79
2008	485.13
2009	496.26
2010	508.66
2011	514.66
2012	517.79
2013	518.73
2014	529.76
2015	545.17
2016	560.84