Year	Number of
1990	60.31
1991	63.08
1992	65.9
1993	68.61
1994	71.13
1995	73.85
1996	75.34
1997	77.04
1998	79
1999	80.92
2000	82.8
2001	87.18
2002	92.06
2003	96.65
2004	101.15
2005	105.72
2006	111.11
2007	116.52
2008	122.17
2009	128.2
2010	134.49
2011	139.33
2012	144.73
2013	150.47
2014	156.95
2015	163.77
2016	171.01