Year	Number of
1990	41.87
1991	41.84
1992	41.74
1993	41.98
1994	42.7
1995	44.08
1996	47.44
1997	52.05
1998	57.8
1999	63.87
2000	69.9
2001	74.15
2002	77.82
2003	80.97
2004	84.54
2005	88.91
2006	93.43
2007	98.74
2008	104.95
2009	111.52
2010	118.33
2011	123.55
2012	128.61
2013	133.33
2014	138.31
2015	143.71
2016	150.44