What is the cost of spilling almost five million barrels of oil into the ocean? How do you measure that cost? In GDP reduction? In lives affected? In environmental impact? And how do you measure the cost when long-term effects are impossible to calculate yet, and when a significant portion of the spilled oil is still unaccounted for? One year since the Deepwater Horizon platform exploded, killing 11 workers, there are measurable effects, and many more unknowns.