Year	Number of
1990	140.22
1991	132.37
1992	125.33
1993	118.91
1994	112.95
1995	107.48
1996	107.55
1997	107.83
1998	108.52
1999	109.41
2000	110.62
2001	114.69
2002	119.07
2003	124.01
2004	129.15
2005	134.61
2006	140.83
2007	147.14
2008	154.41
2009	162.13
2010	170.49
2011	177.31
2012	184.92
2013	193.26
2014	202.02
2015	211.16
2016	220.47