Year	Number of
1990	54.08
1991	56.11
1992	58.18
1993	60.46
1994	62.79
1995	65.28
1996	68.06
1997	71.07
1998	74.18
1999	77.16
2000	80.47
2001	84.13
2002	87.35
2003	91.1
2004	94.68
2005	98.56
2006	102.39
2007	106.29
2008	109.73
2009	114.2
2010	118.09
2011	121.9
2012	125.86
2013	129.44
2014	133.25
2015	137.2
2016	143.15