Well, we measured NPP using satellite data so we took a long time series of satellite data that monitors the amount of plant growth on land. So we meld the satellite data with a lot of climate information and put those into plant growth models which then estimates the amount of net primary production that's on the landscape and accumulates annually. We then took the Food and Agriculture Organization's database of all the food and fiber products generated from plants that were consumed, globally and by country, and we generated models that told us how much plant material you would need on the landscape to generate those end products. That way we got both the satellite-generated supply, planetary supply, adjusted to fit the global planetary demand in terms of food and fiber products, and that way we could look at a balance and see where we are in terms of the balance of supply and demand of plant-based net primary production.