Year	Number
1970	8.2885
1971	8.07299
1973	7.40651
1974	7.83226
1975	7.713
1979	9.07866
1981	9.51139
1982	13.92039
1983	18.77172
1985	17.69806
1986	16.53999
1994	22.98604
2017	30.96962
2018	29.76096