Year	Number
1970	23.13762
1971	22.52125
1972	21.7014
1973	20.51185
1974	21.96758
1976	29.27404
1990	24.78793
1993	26.68461
1994	28.36574
2007	31.56236
2015	31.9738
2016	32.20814
2017	33.2407
2018	33.50124