Year	Number of
1990	67.99
1991	71.13
1992	74.47
1993	77.48
1994	80.86
1995	84.96
1996	88.65
1997	93.04
1998	95.99
1999	96.48
2000	103.02
2001	108.58
2002	110.71
2003	119.3
2004	126.14
2005	131.24
2006	138.29
2007	146.05
2008	153.7
2009	157.72
2010	167.05
2011	176.26
2012	188.09
2013	197.51
2014	214.84
2015	231.99
2016	247.24