Price wars and collusion in the Spanish electricity market

We analyze the time-series of prices in the Spanish electricity market by means of a time varying-transition-probability Markov-switching model. Accounting for changes in demand and cost conditions (which reflect changes in input costs, capacity availability and hydro power), we show that the time-series of prices is characterized by two significantly different price levels. Using a Cournot model among contracted firms, we characterize firms' optimal deviations from a collusive agreement, and identify trigger variables that could be used to discourage deviations. By interpreting the effects of the triggers in affecting the likelihood of starting a price war, we are able to infer some of the properties of the collusive strategy that firms might have followed. (c) 2005 Elsevier B.V. All rights reserved.