The peaking and starting of production decline makes huge difference in the future projections. If we project that a country will increase production three years by 5% a year, but in reality it starts to decline by 5%, it means that the production will be 31% lower than projected. Note: three years, 5% and 31%. If this kind of turn happens, it will crush all predictions for that oil area. And these kind of turns have happened. They have been quite a shock for those countries (take Argentine), especially if they coincide with bad price fluctuations. If investments, economic activity and economic policy is geared for continuing oil production growth, the peaking will mean that the economy falls flat down. That is why the peak is so interesting.

We can really see kind of "Hubbert phases" in many oil producing countries:  an oil euphoria when the curve goes exponential and wild projections of the oil industry growing and money flowing in are made. Liberal economic policy is adopted, currency revalues, importing stuff and taking loan becomes cheap and everbody has fun. At his moment the production peaks, without real warning (OK, some oil engineers may have hinted something). At this moment the oil officials usually make some optimistic statements of increasing investment and boosting production next year because it has been rising before. The plateau is usually not long (it might be less than a year) and the decline begins. The Hubbert curve is mostly more or less symmetric and the oil hangover begins. The drop is steepest in the beginning and the gap of expectations and reality widens rapidly. Nobody has fun any more. Currency collapses, debt becomes a burden, stocks and real estate lose their value. But nobody connects this to the oil depletion. So no lessons are learned. but some rioting is done.