Table 12 Distribution of US schools amoung different periods of construction
Period of construction | Age class | Proportion of schools surveyed (%) |
|---|---|---|
1901-1920 | 80 | 3 |
1921-1930 | 70 | 7 |
1931-1940 | 60 | 5 |
1941-1950 | 50 | 6 |
1951-1960 | 40 | 26 |
1961-1970 | 30 | 24 |
1971-1980 | 20 | 13 |
1981-1990 | 10 | 8 |
1991-2000 | 0 | 9 |