Note that the difficulty curve is logistic, not exponential, because you are creating your own labor pool; older kids not only learn to take care of themselves,

Note that the difficulty curve is logistic, not exponential, because you are creating your own labor pool; older kids not only learn to take care of themselves, but can also be prevailed upon to look after their younger siblings. There is an ultimate ceiling to the labor involved, because your oldest eventually move out; my parents raised eleven children, but the most they had in the house at once was nine.