Year	Number of
1990	71.18
1991	73.68
1992	76.29
1993	79
1994	81.8
1995	84.76
1996	87.63
1997	90.72
1998	93.96
1999	97.25
2000	100.61
2001	103.28
2002	105.86
2003	108.52
2004	111.39
2005	114.61
2006	117.51
2007	120.6
2008	124.05
2009	127.8
2010	131.89
2011	135.57
2012	139.69
2013	144.01
2014	148.62
2015	153.53
2016	159.16