Year	% of population
1963	19.2
1964	19
1965	18.7
1966	19.5
1967	18.5
1968	17.7
1969	17.7
1970	18
1971	18
1972	18.7
1973	17.7
1974	17.5
1975	18
1976	17.7
1977	17.2
1978	17.2
1979	17.2
1980	17.5
1981	18.2
1982	19.2
1983	20.2
1984	19.7
1985	20
1986	19.7
1987	19.7
1988	19.5
1989	19.5
1990	19.7
1991	20.2
1992	20.2
1993	20.5
1994	20
1995	19.5
1996	19.7
1997	19.2
1998	19.5
1999	19.2
2000	18.7
2001	19
2002	19.5
2003	19.5
2004	19.2
2005	19.2
2006	19.2
2007	19.7
2008	19.7
2009	19
2010	19.2
2011	19.5
2012	19.7
2013	19.5
2014	18.7
2015	18.7
2016	19.2
2017	19.7
2018	19.5
2019	19.5
2020	18.2
2021	16.7