I don't think we have a good answer as to why MMS has produced what seem to be such unrealistic production estimates. It seems like the likely reason was that this was the politically desired outcome. It was in 1998 that the IEA (the international organization) made its projection of world oil supply that took into account peak oil considerations. When the USA came up with its optimistic estimates of remaining reserves (not just in the Gulf of Mexico, but in the world as a whole), the IEA dropped its comments about peak oil in its forecasts, and made forecasts based solely on demand. The US EIA has produced optimistic forecasts as long as one can remember, and the high reserve numbers may have helped support these forecasts.