Year	Number of
1990	38.35
1991	41.21
1992	43.66
1993	46.08
1994	48.69
1995	51.41
1996	54.27
1997	57.3
1998	60.65
1999	63.8
2000	67.08
2001	70.23
2002	73.57
2003	77.38
2004	81.17
2005	84.94
2006	88.53
2007	92.19
2008	96.2
2009	100.44
2010	104.89
2011	109.33
2012	114.1
2013	118.98
2014	124.33
2015	129.97
2016	135.4