How sprays are scheduled in US cities, 1980 and 1986
| Spraying schedules | 1980a | 1986b | ||
|---|---|---|---|---|
| # Cities | % | # Cities | % | |
| Regular intervals | 74 | 6 | 45 | 5 |
| Calendar dates | 92 | 8 | 60 | 7 |
| Apparent need | 711 | 62 | 548 | 66 |
| Not at all | 347 | 30 | 234 | 28 |
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