Year	Number
1970	20.73165
1971	20.2256
1972	22.13889
1974	23.81041
1977	24.34799
1978	24.07248
1979	25.24861
1982	35.62286
1983	35.45159
1984	38.53351
1986	37.46026
1987	37.1588
1988	36.57634
1991	28.62796
1993	30.53954
1995	35.49207
1998	39.27845
1999	41.70401
2000	41.147
2001	39.48254
2005	31.05151
2006	29.18213
2008	29.87891
2009	27.70221
2010	25.89606
2011	25.37845
2012	23.9859
2013	28.67592
2015	40.00443
2016	38.03778
2017	34.56294
2018	34.66868