They find that variation in ozone concentrations at levels well below federal air quality standards have a significant impact on productivity. (nber.org)
A design value is the three - year average of pollution concentrations measured at each monitoring location and is used to determine whether a county is in attainment with federal air quality standards. (sciencedaily.com)
We find robust evidence that ozone levels well below federal air quality standards have a significant impact on productivity. (ideas.repec.org)