Year	Number of
1990	27.44
1991	28.05
1992	28.01
1993	27.44
1994	26.5
1995	25.27
1996	27.14
1997	29.61
1998	32.93
1999	36.74
2000	40.93
2001	44.23
2002	47.71
2003	51.7
2004	55.94
2005	60.57
2006	65.38
2007	70.67
2008	76.91
2009	84.03
2010	92.21
2011	100.35
2012	110
2013	120.62
2014	132.25
2015	144.67
2016	160.73