Year	Number of
1990	29.58
1991	30.56
1992	31.64
1993	33
1994	34.53
1995	36.06
1996	37.55
1997	38.51
1998	39.48
1999	40.73
2000	41.75
2001	43.37
2002	45.13
2003	47.24
2004	50.21
2005	54.53
2006	57.79
2007	67.86
2008	74.75
2009	82.63
2010	90.81
2011	99.35
2012	107.08
2013	113.96
2014	120.98
2015	128.49
2016	135.15