Year	Number
1971	34.57133
1972	33.68245
1982	43.23169
1983	42.29809
1984	40.00132
1986	40.90897
1987	40.73307
1988	38.75038
1989	41.20386
1991	40.81242
1992	38.97392
1993	43.23444
1994	42.87582
1998	34.69129
1999	32.87074
2001	30.09904
2002	30.00056
2003	31.86697
2004	31.37395
2005	33.58471
2006	32.87067
2007	34.65493
2015	29.64186
2016	33.62756
2017	27.08486