Year	Number of
1990	44.28
1991	44.97
1992	45.72
1993	46.45
1994	47.29
1995	48.26
1996	49.44
1997	50.89
1998	52.73
1999	55.28
2000	58
2001	60.5
2002	63.23
2003	66.25
2004	69.7
2005	73.4
2006	76.96
2007	80.65
2008	84.55
2009	88.59
2010	93.09
2011	96.29
2012	99.76
2013	103.46
2014	107.41
2015	111.63
2016	115.97