Year	Number of
1990	167.51
1991	169.32
1992	171.45
1993	173.77
1994	176.49
1995	179.71
1996	182.07
1997	184.86
1998	187.67
1999	190.37
2000	193.38
2001	196.15
2002	199.57
2003	203.33
2004	207.35
2005	211.72
2006	217.03
2007	222.71
2008	229.05
2009	235.81
2010	243.13
2011	249.46
2012	256.63
2013	264
2014	271.76
2015	279.46
2016	287.49