Year	Number of
1990	127.1
1991	128.22
1992	129.93
1993	132.86
1994	135.99
1995	137.45
1996	139.81
1997	141.85
1998	146.07
1999	144.09
2000	147.4
2001	152.52
2002	155.83
2003	169.25
2004	171.07
2005	178.11
2006	183.44
2007	191.14
2008	203.96
2009	206.99
2010	213.25
2011	217.01
2012	222.11
2013	228.8
2014	235.61
2015	241.46
2016	248.67