The problem, if you want to call it a problem, is all Hubbert extraction curves are fractal self similar. So some field in Pennsylvania decades ago looks like

The problem, if you want to call it a problem, is all Hubbert extraction curves are fractal self similar. So some field in Pennsylvania decades ago looks like Texas the state decades ago looks like Mexico production "now" looks like world production estimates... may as well just publish one graph for them all. That unusual self similarity of all oil production graphs at all scales and all locations on the planet is kinda the whole point of the topic.