Year	% of population
1977	63.5
1983	56.6
1987	53.1
1993	51.8
2004	48.2
2009	44.7
2011	39.9
2015	37.2
2016	36.8
2017	34.3
2018	32.4
2019	34
2020	34.8
2021	33.1