Year	Number
1970	19.85132
1971	19.69631
1973	22.65423
1974	22.63403
1975	23.06175
1976	23.73865
1977	23.30642
1978	23.31839
1979	22.01728
1995	19.1001
2007	17.77046
2008	17.15864
2009	16.15282
2016	11.65009
2017	11.47558