Year	Number of
1990	153.61
1991	159.66
1992	166.22
1993	173.11
1994	180.4
1995	188.21
1996	195.14
1997	202.35
1998	209.5
1999	216.85
2000	224.64
2001	229.73
2002	234.87
2003	240.1
2004	245.54
2005	251.63
2006	255.74
2007	259.83
2008	264.74
2009	269.99
2010	275.84
2011	281.87
2012	288.41
2013	295.2
2014	302.4
2015	310.05
2016	318.51