Year	Number of
1990	33.07
1991	32.75
1992	32.47
1993	32.12
1994	31.75
1995	31.41
1996	30.93
1997	30.56
1998	30.76
1999	31.76
2000	32.78
2001	32.92
2002	34.02
2003	34.88
2004	36.21
2005	36.39
2006	37.62
2007	38.77
2008	39.63
2009	40.95
2010	41.57
2011	41.81
2012	42.95
2013	43.82
2014	44.71
2015	45.65
2016	46.71