Year	Number of
1990	31.94
1991	33.08
1992	34.52
1993	36.24
1994	37.57
1995	38.95
1996	39.86
1997	40.78
1998	42.01
1999	43.63
2000	45.01
2001	47.58
2002	50.12
2003	52.73
2004	55.62
2005	57.15
2006	58.64
2007	60.35
2008	62.29
2009	64.31
2010	66.3
2011	67.76
2012	69.22
2013	70.85
2014	72.64
2015	74.56
2016	76.22