Year	Number of
1990	38.07
1991	37.86
1992	37.52
1993	37.21
1994	37.01
1995	37.05
1996	37.53
1997	38.33
1998	39.42
1999	40.36
2000	41.33
2001	41.95
2002	42.7
2003	43.55
2004	44.47
2005	45.46
2006	46.57
2007	47.67
2008	48.83
2009	50.08
2010	51.48
2011	52.49
2012	53.64
2013	54.82
2014	56.08
2015	57.39
2016	59.03