When some thing unexpected takes place that affects one economy (or part of an economy) significantly more than the others. This might produce huge problems for policymakers if they're trying to set a macroeconomic plan that really works for both the area impacted by the shock while the unchanged location. By way of example, some economic areas could be oil exporters and therefore highly determined by the price tag on oil, but other areas aren't. If oil price plunges, the oil-dependent location would take advantage of guidelines built to boost demand that could be unsuited into the requirements for the remaining portion of the economic climate. This may be a continuing problem for all responsible for setting the attention price for euro because of the big differences--and different prospective exposures to shocks--among the economies inside the euro zone.