Actually, I've been tracking this closely, and it's some value over 65%--probably 70%.
I am pleased to confirm that the emigration threshold is in fact 75%, as was expected. My city just received its first immigrants, and the region that it received them from had 75% populution before the peasants moved.
To be exact: 4360 (+89 that moved) out of a maximum of 5900. This was yesterday.
Good thing I saw this topic, as I had actually stopped checking. Good timing!
