Year | 2nd generation | 1st generation |
---|---|---|
1900 | 20.8 | 13.7 |
1910 | 20.1 | 14.6 |
1920 | 20.6 | 12.7 |
1930 | 20.1 | 11.3 |
1940 | 18.8 | 8.5 |
1950 | 16.2 | 6.9 |
1960 | 13.8 | 5.6 |
1970 | 12.0 | 4.8 |
1980 | 10.3 | 6.2 |
1990 | 9.6 | 8.2 |
2000 | 10.0 | 11.4 |
2006 | 10.5 | 12.1 |
2010 | 11.3 | 12.7 |
2015 | 12.1 | 13.3 |
2016 | 12.0 | 13.5 |
2017 | 12.0 | 13.7 |
2018 | 12.3 | 14.1 |