Year	Number of
1990	136.44
1991	143.86
1992	149.81
1993	156.47
1994	162.44
1995	168.49
1996	174.36
1997	179.23
1998	184.12
1999	188.07
2000	193.38
2001	197.9
2002	203.42
2003	210.78
2004	217.02
2005	223.7
2006	231.75
2007	239.27
2008	249.67
2009	259.47
2010	271.77
2011	283.68
2012	294.14
2013	307.39
2014	321.3
2015	335.95
2016	351.86