Year	Number of
1990	131.27
1991	135.69
1992	143.23
1993	151.75
1994	160.77
1995	172.4
1996	181.33
1997	193.5
1998	208.19
1999	225.27
2000	243.02
2001	262.69
2002	280.43
2003	301.83
2004	322.53
2005	345.9
2006	369.14
2007	390.95
2008	413.72
2009	439.73
2010	468.26
2011	497.16
2012	527.77
2013	559.64
2014	594.48
2015	630.95
2016	671.89