Year	Number
1970	46.77283
1971	49.61932
1972	47.16955
1973	47.88617
1974	47.99458
1975	48.20911
1976	47.55969
1977	48.1877
1978	48.54414
1979	44.35234
1980	48.56388
1981	48.21651
1982	47.86923
1983	46.50928
1984	46.77766
1985	49.38532
1986	45.62973
1987	45.56304
1988	44.08727
1990	44.01223
1994	41.08401
1995	39.09751
1996	38.19415
1998	44.0078
1999	51.22681
2000	49.87587
2001	48.02502
2002	48.08873
2004	53.54891
2005	56.47904
2006	57.00626
2007	55.35345
2008	54.17641
2010	52.98507
2011	55.86195
2012	49.22433
2014	41.0469
2015	42.74181
2016	43.31661
2017	42.05996