Year	Number of
1990	221.36
1991	222.32
1992	221.56
1993	220.5
1994	220.43
1995	222.24
1996	229.71
1997	240.99
1998	256.27
1999	272.94
2000	290.24
2001	306.04
2002	322.48
2003	340.66
2004	360.61
2005	382.85
2006	403.34
2007	425.62
2008	451.12
2009	478.68
2010	508.38
2011	534.61
2012	562.71
2013	592.26
2014	622.54
2015	653.27
2016	681.31