Year	Number of
1990	15.05
1991	16.03
1992	17.26
1993	18.64
1994	19.98
1995	21.19
1996	22.31
1997	23.05
1998	23.48
1999	23.77
2000	24.03
2001	24.86
2002	26.08
2003	27.63
2004	29.38
2005	31.3
2006	33.06
2007	34.87
2008	37.3
2009	40.98
2010	46.45
2011	50.51
2012	56.59
2013	63.84
2014	71.1
2015	77.56
2016	84.41