Year	Number
1971	27.50432
1972	24.86383
1978	14.47783
1981	13.20762
1983	14.1129
1984	14.46324
1985	14.17111
1986	14.98297
1987	14.84626
1988	14.63631
1989	15.19048
1990	14.44853
1991	15.20543
1992	15.51302
1993	19.45476
1994	17.01522
1995	18.8371
1996	13.90296
1998	15.29046
1999	12.19962
2000	13.63405
2001	13.48482
2011	13.7911
2016	16.64766
2017	15.32851
2018	14.06519