The following five sentences, labeled 1 to 5, relate to a single topic. Four of these sentences can be arranged to form a logical paragraph. Identify the sentence that does not fit with the others and enter its number as your answer.

1. Despite the explicit mandate of price stability, the operationalization of inflation targeting mechanisms by central banks is frequently undermined by significant forecasting uncertainties and protracted transmission lags inherent in monetary policy.
2. Accurate prediction of future price movements remains a formidable challenge, as economic models often struggle to capture non-linear dynamics and the complex interplay of demand-side and supply-side shocks that influence inflation.
3. Moreover, the effectiveness of domestic monetary interventions can be severely constrained by exogenous global factors, such as commodity price volatility or international supply chain disruptions, which are largely beyond a central bank's direct control.
4. The sustained credibility of the monetary authority, crucial for anchoring inflation expectations, is perpetually tested by persistent deviations from the target, potentially weakening the forward guidance mechanism.
5. Historically, periods of unchecked hyperinflation have often preceded profound social unrest and political upheaval, demonstrating that sustained price instability carries significant consequences beyond merely economic metrics, impacting societal cohesion.