Year	Number of
1990	55.48
1991	57.69
1992	60.13
1993	62.82
1994	65.7
1995	68.8
1996	70.98
1997	73.38
1998	75.99
1999	78.81
2000	81.89
2001	84.45
2002	87.29
2003	90.39
2004	93.73
2005	97.38
2006	100.04
2007	102.85
2008	106.04
2009	109.49
2010	113.27
2011	117.57
2012	122.24
2013	127.24
2014	132.56
2015	138.21
2016	144.17