Year	Number of
1990	44.05
1991	44.82
1992	49.12
1993	53.32
1994	56.55
1995	57.8
1996	58.61
1997	62.03
1998	67.76
1999	75.83
2000	82.92
2001	90.63
2002	97.56
2003	104.26
2004	107.23
2005	109.48
2006	112.7
2007	115.33
2008	121.41
2009	126.11
2010	128.58
2011	133.57
2012	137.1
2013	142.31
2014	144.67
2015	143.39
2016	143.39