OLS and IV regression results for effect of ozone on respiratory illnesses
| 1 OLS | 2 IV | 3 IV | |
|---|---|---|---|
| A. First stage | |||
| Boat traffic / 100,000 | – | 4.608** | 4.409** |
| – | [0.029] | [0.044] | |
| Boat traffic / 100,000)*distance | – | −0.198** | −0.181** |
| – | [0.001] | [0.003] | |
| (Boat traffic / 100,000)*distance2)*1000 | – | – | −0.293** |
| – | – | [0.048] | |
| B. Second stage | |||
| Eight-hour ozone | 0.113** | 0.454** | 0.442** |
| [0.023] | [0.162] | [0.162] | |
| Wu-Hausman F test (1,1927109) | – | 4.820 | 4.485 |
| P-value | – | 0.028 | 0.034 |
| Percent effect | 1.16 | 4.66 | 4.54 |
Notes:
↵* significant at 5 percent,
↵** significant at 1 percent. N = 1,927,187 in all regressions. Robust standard errors clustered by date in brackets. Dependent variable is the number of respiratory related hospital admissions per day, zip code, and age category. All regressions include controls for carbon monoxide, nitrogen dioxide, maximum temperature, minimum temperature, precipitation, wind speed, humidity, cloud cover, age dummies, year-month dummies, day of week dummies, cubic day trend, and zip code fixed effects. “Percent effect” is the estimated percentage change in the dependent variables from 0.01 ppm increase in ozone based on the estimated ozone coefficient.