Year	Number of
1990	37.57
1991	37.89
1992	37.98
1993	37.9
1994	37.79
1995	37.79
1996	38.42
1997	39.28
1998	40.39
1999	41.68
2000	43.15
2001	44.63
2002	46.31
2003	48.1
2004	49.88
2005	51.65
2006	53.08
2007	54.34
2008	55.55
2009	56.74
2010	58.02
2011	59.7
2012	61.51
2013	63.41
2014	65.38
2015	67.43
2016	69.92