All data used are publicly available. Demographic data are available via IPUMS National Historic Geographic Information Systems [<a href="http://www.nhgis.org/" target="_blank">www.nhgis.org</a>]; air pollution estimates are available via the EPA CACES project [<a href="http://www.caces.us/" target="_blank">www.caces.us</a>]).
All data used are publicly available. Demographic data are available via IPUMS National Historic Geographic Information Systems [<a href="http://www.nhgis.org/" target="_blank">www.nhgis.org</a>]; air pollution estimates are available via the EPA CACES project [<a href="http://www.caces.us/" target="_blank">www.caces.us</a>]).
All data used are publicly available. Demographic data are available via IPUMS National Historic Geographic Information Systems [<a href="http://www.nhgis.org/" target="_blank">www.nhgis.org</a>]; air pollution estimates are available via the EPA CACES project [<a href="http://www.caces.us/" target="_blank">www.caces.us</a>]).
All data used are publicly available. Demographic data are available via IPUMS National Historic Geographic Information Systems [<a href="http://www.nhgis.org/" target="_blank">www.nhgis.org</a>]; air pollution estimates are available via the EPA CACES project [<a href="http://www.caces.us/" target="_blank">www.caces.us</a>]).
All data used are publicly available. Demographic data are available via IPUMS National Historic Geographic Information Systems [<a href="http://www.nhgis.org/" target="_blank">www.nhgis.org</a>]; air pollution estimates are available via the EPA CACES project [<a href="http://www.caces.us/" target="_blank">www.caces.us</a>]).