&gt; Why specifically would they want the growth of their investments to follow the rule that the derivative of the revenue is proportional to the revenue?<p>Well, I think more precisely they want the growth to be <i>at least</i> exponential; they&#x27;d be happy with super-exponential growth (increasing, rather than constant, <i>k</i> over subsequent intervals.)<p>They also want a minimum value of <i>k</i>.