Year	Number of
1990	155.65
1991	159
1992	162.29
1993	165.58
1994	169.1
1995	173.02
1996	176.97
1997	181.22
1998	185.69
1999	190.44
2000	195.59
2001	200.79
2002	206.39
2003	212.36
2004	218.72
2005	225.59
2006	233.28
2007	241.22
2008	250.02
2009	259.35
2010	269.44
2011	278.92
2012	288.92
2013	299.64
2014	310.87
2015	322.59
2016	335.45