Economic geography is the study of the widely varying economic conditions across the earth. This aspect of economics was intensely studied by Ellsworth Huntington, a professor of economics at Yale University in the early 20th century.
He noted that the Northern, cold regions like the U.S., Britain, Europe and Japan had large, well-developed economies while the hot, tropical countries were less well endowed—the so-called equatorial paradox. Huntington ascribed the differences in economic performance to differences in climate. Some economists are uncomfortable with this idea.
According to Huntington, these differences in economic performance also affected political structures—tropical states tend to have unstable political histories.
Other factors in this model affecting economic performance are access to the sea and the presence of raw materials like oil. Singapore, for example, occupies a key position as a seaport, while the wealth of Saudi Arabia depends almost entirely on oil.