Year	% of population
1968	8.2
1969	9.5
1970	8.7
1971	10
1972	10.7
1973	8.7
1974	10
1975	9.5
1976	9.2
1977	9.2
1978	10.2
1979	9.2
1980	10.2
1981	12
1982	11.7
1983	11.7
1984	12
1985	12
1986	13
1987	13.5
1988	13
1989	13.7
1990	14.5
1991	14.5
1992	15.7
1993	16.2
1994	15.5
1995	15.2
1996	15.2
1997	15.5
1998	15.2
1999	15.5
2000	14.5
2001	14.5
2002	13.7
2003	14
2004	13.7
2005	14.5
2006	14.2
2007	14.5
2008	14.7
2009	14
2010	13.2
2011	13.5
2012	13.2
2013	13.2
2014	13.7
2015	14
2016	14
2017	14.2
2018	14.5
2019	14.5
2020	13.2
2021	13.2