Year	Number of
1990	263.66
1991	268.9
1992	274.42
1993	281.38
1994	288.95
1995	297.13
1996	294.11
1997	290.95
1998	287.97
1999	285.53
2000	283.76
2001	295.21
2002	307.2
2003	320.69
2004	334.45
2005	348.68
2006	368.83
2007	390.18
2008	413.37
2009	438
2010	464.81
2011	488.77
2012	513.81
2013	540.52
2014	568.97
2015	599.89
2016	620.66