Year	Number of
1990	136.65
1991	141.38
1992	146.16
1993	151.13
1994	156.3
1995	161.88
1996	166.13
1997	170.81
1998	176.2
1999	181.63
2000	187.21
2001	192.07
2002	197.32
2003	203.52
2004	210.2
2005	217.66
2006	223.92
2007	230.38
2008	237.67
2009	246.01
2010	255.78
2011	263.46
2012	272.41
2013	281.85
2014	291.93
2015	302.5
2016	313.39