Year	Number of
1990	29.63
1991	30.65
1992	31.77
1993	33
1994	34.28
1995	35.65
1996	36.65
1997	37.67
1998	38.78
1999	39.86
2000	40.95
2001	42.72
2002	44.57
2003	46.57
2004	48.73
2005	51.12
2006	52.45
2007	53.88
2008	55.52
2009	57.19
2010	58.91
2011	60.21
2012	61.62
2013	63.2
2014	64.96
2015	66.92
2016	68.83