[economist420]

? Umm. An S curve IS exponential. It's exponential growth, followed by exponential decay.

[antisthenes]

No, it's not. An S-curve is logarithmic.

It may mimic a quadratic curve in smaller values, but for pragmatic purposes it becomes asymptotic to some arbitrarily chosen value, in most cases.

There is no decay either, because the value of y is still always increasing.