Year	Number of
1990	24.83
1991	27.3
1992	30.13
1993	33.05
1994	36.42
1995	40.25
1996	43.5
1997	47.15
1998	51
1999	55.17
2000	59.87
2001	62.98
2002	67.03
2003	73.42
2004	83.32
2005	97.88
2006	111.73
2007	131.34
2008	155.38
2009	180.93
2010	206.07
2011	237.17
2012	266.34
2013	294.67
2014	324.47
2015	358.32
2016	398.22