Extent of biological control in US cities, 1980 and 1986.
| Classification | 1980 Number reporting | Response % yes | 1986 Number reporting | Response % yes |
|---|---|---|---|---|
| Total all cities | 1012 | 25 | 747 | 25 |
| Population group | ||||
| Over 1,000,000 | 5 | 40 | 2 | 50 |
| 500,000 | 12 | 25 | 8 | 50 |
| 250,000 | 25 | 36 | 17 | 29 |
| 100,000 | 60 | 37 | 56 | 30 |
| 50,000 | 131 | 32 | 112 | 29 |
| 25,000 | 228 | 28 | 196 | 29 |
| 10,000 | 179 | 21 | 310 | 20 |
| 5,000 | 36 | 19 | 23 | 17 |
| less than 5,000 | 13 | 19 | 23 | 23 |
| Geographic Region | ||||
| Northeast | 229 | 16 | 150 | 16 |
| North Central | 338 | 24 | 241 | 29 |
| South | 208 | 24 | 168 | 22 |
| West | 237 | 36 | 188 | 29 |