Year	Number of
1990	71.9
1991	74.82
1992	77.77
1993	80.78
1994	83.98
1995	87.47
1996	91.84
1997	96.53
1998	101.48
1999	106.86
2000	112.75
2001	118.56
2002	124.7
2003	131.27
2004	138.35
2005	146.11
2006	152.41
2007	158.97
2008	166.15
2009	173.83
2010	182.21
2011	189.72
2012	197.65
2013	205.87
2014	214.69
2015	224.21
2016	235.54