It was most likely different due to the region's status in the world and it's economical standpoint. If the region is short on food and supplies, labour would most likely be more intensive to get back on the flow with more food and supplies. If a different region was all set on everything and didn't need anything extra, the forced labour would be held back a little, easing the work load on it's people. But once resources go down, forced labour would go back up!