JD apparently knows nothing about the mathematical concept of an asymptote.

Oh, I forgot, asymptotes are features of junk science.

Seriously, it's like asking why log-log graph paper does not have any zero intercepts.

Speaking of log graphs, I was thinking that, as the wild swings in the curve for low cummulative output are exagerated (the ratio is more sensetive to chages in production for low cummulatives), the opposite might be true further out on the graph (the curve may not be sensitive enough to be enlightening for large cummulative values).  Perhaps putting these data on log paper, or some other non-linear scale, might be more illustrative.