[Truper]

What you're missing is that its the growth/death scale that affects supplies. Supplies are generated in provinces based on the population and the terrain. Farmlands = more supplies, wasteland = less. Additional supplies are generated by castle provinces, and radiate out from them to a 4 province radius, with diminishing returns over increasing distance. Supplies available in a province based on the above are also affected by growth/death. Growth = more supplies, death = less. But this Last is not true for Abyssia, whose supplies are not affected by the growth/death scale. If Abyssia takes death, they won't have the supply problems other nations would have, but their population will still decline, and so will their income, which is based on population.