Year	Number of
1990	140.5
1991	143.17
1992	146.16
1993	149.54
1994	153.16
1995	157.18
1996	160.08
1997	163.35
1998	167.22
1999	171.26
2000	175.66
2001	181.29
2002	187.39
2003	194.55
2004	201.92
2005	209.69
2006	217.38
2007	225.15
2008	234.15
2009	243.64
2010	253.93
2011	262.53
2012	271.84
2013	281.72
2014	292.06
2015	302.87
2016	313.17