Here’s a version, then, that does not rely on the number of non-slaves: If the growth rate of the number of slaves was x, and now it is x/2, then I’d say the situation has improved, even if the number of slaves is higher now.
Here’s a version, then, that does not rely on the number of non-slaves: If the growth rate of the number of slaves was x, and now it is x/2, then I’d say the situation has improved, even if the number of slaves is higher now.