States are part of countries, and countries may be grouped by other areas, like continents, hemispheres, or a political or ...

The U.S. eliminated measles in 2000—but that hard-won achievement is now under threat. To contain the current outbreak, some ...

North America is the third largest continent in the world. It is located in the Northern Hemisphere. The north of the continent is within the Arctic Circle and the Tropic of Cancer passes through ...

We study the causes of “nutritional inequality”: why the wealthy eat more healthfully than the poor in the United States. Exploiting supermarket entry, household moves to healthier neighborhoods, and ...