Year	Number of
1990	27.78
1991	29.07
1992	30.35
1993	31.48
1994	33.68
1995	36.27
1996	39.67
1997	42.36
1998	44.39
1999	46.47
2000	48.33
2001	50.5
2002	52.26
2003	53.89
2004	54.25
2005	55.73
2006	56.94
2007	59.13
2008	61.27
2009	63.03
2010	64.78
2011	69.44
2012	73.64
2013	76.84
2014	81.35
2015	85.51
2016	91.17