Year	Number of
1990	68.9
1991	69.51
1992	69.95
1993	70.2
1994	70.48
1995	70.88
1996	73.42
1997	76.13
1998	79.07
1999	82.27
2000	85.8
2001	90.76
2002	96.3
2003	102.61
2004	109.2
2005	115.93
2006	119.65
2007	123.17
2008	127.06
2009	131.36
2010	136.36
2011	138.48
2012	141.26
2013	144.48
2014	147.83
2015	151.09
2016	153.95