point of diminishing return
- That point at which total production begins to increase at a decreasing rate with successive application of inputs.
http://www.marketingpower.com/mg-dictionary-view2415.phplaw of diminishing return
- After a certain point has been reached, each successive application of a factor of production will add less to total output than before
[And worst of all]
point of negative return
- That point at which total production decreases absolutely with successive applications of inputs.
Or in other words , have you ever been sweeping a floor and noticed a little line of dirt that marked the frount edge of the dustpan?
When you resweep you get that up , except for a very small line that marks the frount of the dustpan.
Repeating this iteration forever will continually reduce the little line without ever eliminateing it.
I beleive you could apply Calculus to this and determine a rate , if you cared to , but that would be far beyond any expected return.