Industry agglomeration, when businesses in the same industry group together, is influenced by factors within companies as well as between them. By studying U.S. census data, researchers divided factors influencing agglomeration into those within firms and those shared between firms. They found that, for most industries and locations, factors within companies play only a small role in industry clustering. However, for certain industries and in close proximity, internal factors contribute significantly to why businesses gather together. This suggests that while businesses being close to each other does help them, the reasons for this closeness can differ depending on the industry and how close the businesses are to each other.