Year	per 1000 people
1960	0.081
1965	0.19
1970	0.269
1975	0.269
1979	0.331
1981	0.332
1984	0.691
1988	0.829
1990	0.7
1991	0.411
1995	0.65
1997	0.832
2000	0.589
2005	0.39