Year	Number of
1990	146.6
1991	150.03
1992	153.19
1993	155.05
1994	156.73
1995	159.74
1996	162.48
1997	165.96
1998	169.62
1999	171.93
2000	174.5
2001	179.63
2002	186.13
2003	191.78
2004	198.6
2005	205.55
2006	212.22
2007	217.84
2008	222.68
2009	228.22
2010	233.5
2011	238.29
2012	242.46
2013	245.72
2014	249.48
2015	253.13
2016	258.22