Year	per 1,000 people
1960	1.35531914234161
1970	1.35570001602173
1975	1.42200005054474
1988	0.906300008296967
1990	0.7534999847
1997	0.400000006
2000	0.42
2001	0.42
2002	0.42
2003	0.42
2004	0.42
2013	0.87
2014	0.87
2015	0.87
2016	0.87
2017	0.87