Year	Number of
1990	222.5
1991	225.75
1992	229.2
1993	238.02
1994	239.39
1995	242.64
1996	247.76
1997	250.61
1998	255.48
1999	259.7
2000	265.02
2001	271.29
2002	280.07
2003	291.53
2004	300.19
2005	308.95
2006	318.02
2007	327.36
2008	341.61
2009	357.88
2010	375.32
2011	391.97
2012	410.39
2013	428.22
2014	447.49
2015	468.18
2016	490.72