A common method of estimating remaining reserves is decline curve analysis. There is a tendency to believe that estimates of remaining reserves will improve (become closer to truth) as more production data becomes available. This is not necessarily true even though our estimate of the ultimate recovery will generally improve with increased production history. The use of curve fitting techniques will not necessarily increase the accuracy of estimating remaining reserves and may, in some cases, lead to unreasonable answers. Reserve estimates will also vary among reserve estimators using the same data. This variance can be significant as demonstrated by the results of a controlled experiment presented in this paper.