Year	Number of
1990	57.84
1991	56.8
1992	58.68
1993	60.87
1994	62.66
1995	66.16
1996	67.22
1997	70.22
1998	73.73
1999	77.81
2000	81.57
2001	87.08
2002	90.58
2003	96.52
2004	101.25
2005	107.45
2006	113.69
2007	119.14
2008	124.41
2009	131.02
2010	138.34
2011	145.72
2012	153.54
2013	162.07
2014	170.96
2015	180.16
2016	189.33