Under which conditions does electoral volatility increase? The evidence produced so far points to economic shocks as a main factor to explain the change in votes from one party to another. Nevertheless, these studies usually have little or no consideration of the difference between volatility within the current party-system equilibrium (votes changing among parties in the parliament), and volatility out of the equilibrium (votes changing to new or outsider parties). We focus on legislative elections of 16 Western European countries since the II World War. We show that a rise of unemployment or a slower GDP growth generates volatility within the equilibrium. But if these situations are maintained in time, volatility outside the equilibrium will rise, generating the entry/exit of parties. Moreover, an external, explicit and formal intervention in the economic policy decisions, such as those provoked by a loan or a bailout including conditionality from an external organization, will deep these effects. Overall, the direction suggested by the mentioned findings is quite straightforward: long-lasting shocks can provoke structural changes in the European party systems, especially in Southern Europe, strongly affected by the present economic crises.
