Year	Number of
1990	243.4
1991	254.18
1992	268.82
1993	284.73
1994	298.8
1995	316.12
1996	330.25
1997	344.64
1998	363.34
1999	380.67
2000	399.88
2001	397.07
2002	394.8
2003	396.58
2004	399.01
2005	416.53
2006	429.18
2007	442.34
2008	455.28
2009	468
2010	480.44
2011	490.7
2012	502.06
2013	510.98
2014	523.45
2015	538.7
2016	558