Year	Number of
1990	30.89
1991	31.56
1992	32.57
1993	33.57
1994	34.97
1995	36.46
1996	38.06
1997	38.89
1998	40.18
1999	41.71
2000	43.24
2001	44.76
2002	45.62
2003	46.67
2004	48.35
2005	49.53
2006	50.74
2007	51.98
2008	53.62
2009	55.41
2010	57.28
2011	59
2012	61.06
2013	63.15
2014	65.28
2015	67.61
2016	70.24