Year	Number
1971	34.21573
1972	32.91062
1973	27.97946
1974	29.43764
1975	28.66233
1976	26.67078
1977	24.45021
1985	15.06734
1991	23.51117
1992	25.66588
1993	27.1655
1994	28.2574
1995	30.69641
1997	31.31113
2013	17.55105
2014	17.51293
2016	18.6938
2017	19.00886