Year	Number of
1990	30.98
1991	32
1992	33.15
1993	34.3
1994	36.1
1995	37.94
1996	39.98
1997	40.95
1998	41.62
1999	43.45
2000	46.25
2001	48.21
2002	50.82
2003	54.52
2004	57.7
2005	60.3
2006	61.6
2007	63.77
2008	66.51
2009	69.31
2010	71.46
2011	74.47
2012	78.2
2013	80.91
2014	83.56
2015	86.31
2016	88.94