Year	per 1,000 people
1970	0.155100002884865
1980	0.215800002217293
1981	0.225199997425079
1985	0.287800014019012
1990	0.3041999936
1991	0.3080999851
1994	0.3048999906
1999	0.3000000119
2001	0.3
2002	0.34
2005	0.3
2011	0.6
2014	0.6
2015	0.77
2016	0.79