Quantifying company-level impacts – calculation of median footprint sizes by facility category:
We estimated a median footprint size for each asset facility category in the S&P Physical Assets Database. For each category, asset locations were randomly selected for measurement in GIS. If a selected asset’s presence was visually detected and verified with high-resolution satellite imagery, its physical footprint was traced and measured. For all but two facility categories, areas were measured. The two remaining categories (“transmission line” and “natural gas pipeline”) were linear, thus their assets’ widths were measured instead. Between two and 46 assets were sampled for each facility category. The sampled assets’ measurements were used to calculate median footprint sizes (areas or widths) for each category.
For non-linear assets, the point location or each asset was buffered to create a circle of the appropriate area for its category.
For the linear assets, a minimum spanning tree approach was used to connect multiple point locations by unique asset number. Then, the calculated median width was applied to create footprints.
Table S1. Number of assets per S&P Physical Assets Database facility category in analysis. Assets within facility categories may fall under multiple sectors, as sectors are assigned the company level based on a company’s principal business activity.