Year	Number of
1990	34.69
1991	35.84
1992	37.13
1993	38.59
1994	40.11
1995	41.7
1996	43.32
1997	44.97
1998	46.76
1999	48.65
2000	50.72
2001	52.02
2002	53.44
2003	55.08
2004	56.82
2005	58.71
2006	60.46
2007	62.24
2008	64.12
2009	66
2010	67.87
2011	69.85
2012	71.91
2013	73.95
2014	76.26
2015	78.94
2016	81.87