Year	Number of
1990	211.99
1991	213.53
1992	213.84
1993	214.25
1994	218.07
1995	224.32
1996	230.38
1997	239.25
1998	247.33
1999	255.42
2000	262.94
2001	269.6
2002	277.12
2003	283.12
2004	288.6
2005	292.81
2006	300.55
2007	307.01
2008	312.14
2009	316.48
2010	323.8
2011	327.56
2012	331.84
2013	334.61
2014	335.86
2015	337.29
2016	338.19