Year	Number of
1990	131.48
1991	133.74
1992	133.46
1993	133.77
1994	136.93
1995	139.07
1996	141.89
1997	139.1
1998	139.06
1999	142.41
2000	148.04
2001	153.97
2002	159.75
2003	166.35
2004	172.63
2005	178.42
2006	184.64
2007	190.91
2008	197.64
2009	204.77
2010	212.1
2011	218.9
2012	225.96
2013	232.87
2014	239.45
2015	245.59
2016	251.95