Year	Number of
1990	31.78
1991	32.63
1992	33.63
1993	34.65
1994	36.3
1995	38.05
1996	40.08
1997	41.03
1998	41.72
1999	43.68
2000	46.57
2001	48.48
2002	51
2003	54.58
2004	57.76
2005	60.42
2006	61.68
2007	63.74
2008	66.35
2009	68.87
2010	70.7
2011	73.59
2012	77.33
2013	80.18
2014	82.96
2015	85.95
2016	88.94