The article explores how groups of industries working closely together in the same area can boost productivity in regions. They looked at past studies and found that when different or similar industries cluster together, they can share resources, workers, and ideas, leading to increased productivity. Sharing these benefits can happen when industries are alike or different. In the past, researchers mainly used external economies of scale to measure these effects, but now they are using the closeness of businesses in a region to study how productivity increases.