communication in repeated games with private monitoring abstract the paper considers repeated games where each player can be observed by only a subset of the other players and where players can make public announcements about the behavior of the players they observed we address the following question what is the minimal level of observability that is required to obtain efficient outcomes the main result is that the limit set of sequential equilibrium payoffs when the discount factor tends to one contains the set of individual rational payoffs whenever each player is observed by at leasttwoother players journal of economic literatureclassification number c73

price dispersion and incomplete learning in the long run abstract in each period a seller chooses a price and the customer for that period buys either one unit or nothing the relationship between price and purchase probability is one of two linear functions it is shown that the seller behaving optimally does not necessarily learn which function is the actual relationship since there can be a positive probability of sequences of prices converging to the price at which the two functions give the same purchase probability

a study of collusion in first price auctions this paper examines the bidding for school milk contracts in florida and texas during the 1980s in both states firms were convicted of bid rigging the data and legal evidence suggest that the cartels in the two states allocate contracts in different ways one cartel divides the market among members while the other cartel also uses side payments to compensate members for refraining from bidding we show that both forms of cartel agreements are almost optimal provided the number of contracts is sufficiently large in the auction the cartel bidder may face competition from non cartel bidders the presence of an optimal cartel induces an asymmetry in the auction the selected cartel bidder is bidding as a representative of a group and has on average a lower cost than a non cartel bidder the data support the predicted equilibrium bidding behaviour in asymmetric auctions in accordance with optimal cartels

demand response application by strategic wind power producers this paper considers a wind power producer playing strategically in a day ahead market while willing to set demand response dr contracts with a dr aggregator to this end a bilevel problem including a single leader and two followers is formulated the wind power producer is the leader aiming at maximizing its profit through offering into a day ahead market and clearing its deviation in a balancing market the strategic behavior of the producer in the day ahead market is modeled through the market clearing process follower 1 in addition the dr aggregator behavior is modeled through a revenue function in which the aggregator is able to sell its dr product to the wind power producer other competitors and the day ahead market follower 2 the overall problem is a stochastic mathematical program with equilibrium constraints mpec in which wind power production and imbalance prices are associated with uncertainty the problem is then transformed into a linear programming approach a case of the nordic market is chosen to assess the validity of the given problem

collusion with almost no information we analyze noncooperative collusion in an infinitely repeated bertrand game where each of the n firms receives a privately observed i i d cost shock in each period and firms only and privately observe whether they have won the unit mass of consumers no other information is available and no communication is allowed we prove that there exist equilibria in private strategies approximating first best profits when firms are sufficiently patient in particular productive efficiency obtains in the limit

tacit collusion in repeated auctions abstract this paper considers the question of tacit collusion in repeated auctions with independent private values and with limited public monitoring mcafee and mcmillan show that the extent of collusion is tied to the availability of transfers monetary transfers allow cartels to extract full surplus a folk theorem proved by fudenberg et al econometrica 62 1994 997 1039 shows that transfers of future payoffs are almost as good if players are patient and communicate before auctions we ask how the scope of collusion is affected if players dispense with explicit communication and their monitoring is limited collusion better than bid rotation is still feasible but full surplus cannot be extracted this constraint becomes less severe with more players and large cartels can become asymptotically efficient even with very limited monitoring

on the market impact of wind energy forecasts this paper presents an analysis of how day ahead electricity spot prices are affected by day ahead wind power forecasts demonstration of this relationship is given as a test case for the western danish price area of the nord pool s elspot market impact on the average price behaviour is investigated as well as that on the distributional properties of the price by using a non parametric regression model to assess the effects of wind power forecasts on the average behaviour the non linearities and time variations in the relationship are captured well and the effects are shown to be quite substantial furthermore by evaluating the distributional properties of the spot prices under different scenarios the impact of the wind power forecasts on the price distribution is proved to be considerable the conditional price distribution is moreover shown to be non gaussian this implies that forecasting models for electricity spot prices for which parameters are estimated by a least squares techniques will not have gaussian residuals hence the widespread assumption of gaussian residuals from electricity spot price models is shown to be inadequate for these model types the revealed effects are likely to be observable and qualitatively similar in other day ahead electricity markets significantly penetrated by wind power

the regulating power market on the nordic power exchange nord pool an econometric analysis abstract what differentiates the structure of nord pool from other power exchanges around the world is the way the balance from the spot market is maintained until the actual physical delivery takes place via the regulating power market in norway this paper reveals the pattern of the prices on the regulating power market by analysing the cost of being unable to fulfil the commitments made on the spot market some power producers with unpredictable fluctuations e g wind will need to buy regulation services the disclosed pattern implies that these producers must pay a limited premium of readiness in addition to the spot price this premium is independent of the amount of regulation the level of the premium of readiness for down regulation is shown to be strongly influenced by the level of the spot price on the other hand it is demonstrated that the premium for up regulation is less correlated to the spot price furthermore it is found that the amount of regulation affects the price of regulating power for up regulation more strongly than it does for down regulation the disclosed cost of using the regulating power market is a quadratic function of the amount of regulation this asymmetric cost may encourage bidders with fluctuating production to be more strategic in their way of bidding on the spot market by using such strategies the extra costs for example wind power needed to counter unpredictable fluctuations may be limited

maximizing profit of a wind genco considering geographical diversity of wind farms uncertainty and geographical diversity of wind speeds create risk for a wind power generation company wgenco to make the maximum profit from power market trading a probabilistic approach is proposed to estimate the profit of a wgenco considering geographical diversity and uncertainty of wind speeds and market prices the objective of the optimization problem is to assist a wgenco to do the optimal bidding in market trading in order to make the maximum profit under various market and wind speed uncertainties the point estimate method pem has been improved to facilitate stochastic modeling of the aggregated power output of wind turbine generators in different locations in the problem formulation the principal component analysis pca is used to manage correlated wind speeds

trading wind generation from short term probabilistic forecasts of wind power due to the fluctuating nature of the wind resource a wind power producer participating in a liberalized electricity market is subject to penalties related to regulation costs accurate forecasts of wind generation are therefore paramount for reducing such penalties and thus maximizing revenue despite the fact that increasing accuracy in spot forecasts may reduce penalties this paper shows that if such forecasts are accompanied with information on their uncertainty i e in the form of predictive distributions then this can be the basis for defining advanced strategies for market participation such strategies permit to further increase revenues and thus enhance competitiveness of wind generation compared to other forms of dispatchable generation this paper formulates a general methodology for deriving optimal bidding strategies based on probabilistic forecasts of wind generation as well as on modeling of the sensitivity a wind power producer may have to regulation costs the benefits resulting from the application of these strategies are clearly demonstrated on the test case of the participation of a multi mw wind farm in the dutch electricity market over a year

simulating the impact of wind production on locational marginal prices this paper analyzes the impact of wind production on the locational marginal prices of a fully competitive pool based electricity market wind productions are modeled as negative loads and characterized by historical data records the analysis pertains to the structural relationship between wind production and locational marginal prices and disregards the collateral effect of strategic offering the study presented allows a statistical characterization of locational marginal prices as a function of the statistical data of the wind plants and the structure of the considered electric energy system

private monitoring in auctions abstract we study infinitely repeated first price auctions in which a bidder only learns whether or not he won the object while repetition of the stage game equilibrium is the unique nash equilibrium in public strategies with patient bidders there are simple nash equilibria in private strategies that improve on bid rotation sequential rationality is appropriately captured by essentially perfect bayesian equilibrium epbe which ignores behavior after irrelevant histories our main result is the construction of epbea that improve upon bid rotation assuming symmetry the exclusionary schemes of skrzypacz and hopenhayn tacit collusion in repeated auctions j econ theory 114 2004 153 169 including asymptotically efficient ones are supported as epbea

curtailment of renewable generation economic optimality and incentives the loss from curtailing generation based on renewable energy sources is generally seen as an unacceptable solution by the public the main argument is that it is a loss of green energy and an economic loss to curtail generation with near zero marginal costs however this view could lead to overinvestment in grid infrastructure and underinvestment in renewable energy sources this article argues that some curtailment of fluctuating variable generation is optimal we address the possible contributions to total curtailment from involuntary and voluntary curtailment the costs of curtailment in terms of lost generation are discussed based on market price and support levels including the rationale for compensating generators for losses the extent of actual curtailment is illustrated by examples from different global markets in general both the value of the curtailed energy and the amount of curtailed energy relative to total fluctuating generation is low but rising single generators may be affected considerably if insufficient compensation measures are in place in the future optimal curtailment will increase along with an increased share of fluctuating renewable generation extending renewable generation comparatively cheaply can be achieved by the installation of additional capacity at offshore locations until optimal curtailment levels are reached

modeling real time balancing power market prices using combined sarima and markov processes this paper describes modeling of real time balancing power market prices by using combined seasonal auto regressive integrated moving average sarima and discrete markov processes the combination of such processes allows generation of price series with periods where no demand for balancing power exists the purpose of the model is simulation of prices to construct scenario trees representing possible realization of the stochastic prices such scenario trees can be used in planning models based on stochastic optimization to generate bid sequences to the balancing market the spread of the prices in the tree and the shape of the scenarios are of central importance model parameter estimation methods reflecting the demands on scenario trees have therefore been used the proposed model is also applied to data from the nordic power market the conclusion of this paper is that the developed model is appropriate for modeling real time balancing power prices

bidding in sequential electricity markets the nordic case abstract for electricity market participants trading in sequential markets with differences in price levels and risk exposure it is relevant to analyze the potential of coordinated bidding we consider a nordic power producer who engages in the day ahead spot market and the hour ahead balancing market in both markets clearing prices and dispatched volumes are unknown at the time of bidding however in the balancing market the market participant faces an additional risk of not being dispatched taking into account the sequential clearing of these markets and the gradual realization of market prices we formulate the bidding problem as a multi stage stochastic program we investigate whether higher risk exposure may cause hesitation to bid into the balancing market furthermore we quantify the gain from coordinated bidding and by deriving bounds on this gain assess the performance of alternative bidding strategies used in practice

the microeconomics of market making this paper examines the influence of risk aversion on the pricing policies of a market maker for securities it is shown that a market maker s bid ask spread can be decomposed into a portion for the known limit orders a risk neutral adjustment for expected market orders and a risk adjustment for market order and inventory value uncertainty it is dem onstrated that a risk averse market maker may set a smaller spread than a risk neutral specialist finally this paper demonstrates the pervasive role of inventory in affecting both the placement and size ofthe spread

a robust folk theorem for the prisoner s dilemma we prove the folk theorem for the prisoner s dilemma using strategies that are robust to private monitoring from this follows a limit folk theorem when players are patient and monitoring is sufficiently accurate but private and possibly independent any feasible individually rational payoff can be obtained in sequential equilibrium the strategies used can be implemented by finite randomizing automata journal of economic literature classification numbers c72 c73 d82

bidder collusion at forest service timber sales allegations of bidder collusion at forest service timber sales in the pacific northwest were common in the 1970s of course prices may be low for reasons other than collusion we formulate an empirical model that allows for both bidder collusion and supply effects and in which we control for demand conditions noncooperative behavior in which a single unit is sold the standard auction model is a special case it is found to be definitively outperformed by a model of collusion we also find that supply effects are dominated by collusion in determining the winning bids in the market

opportunity cost bidding by wind generators in forward markets analytical results wind generation must trade in forward electricity markets based on imperfect forecasts of its output and real time prices when the real time price differs for generators that are short and long the optimal forward strategy must be based on the opportunity costs of charges and payments in real time rather than a central estimate of wind output we present analytical results for wind s optimal forward strategy in the risk neutral case the optimal strategy is determined by the distribution of real time available wind capacity and the expected real time prices conditioned on the forward price and wind out turn our approach is simpler and more computationally efficient than formulations requiring specification of full joint distributions or a large set of scenarios informative closed form examples are derived for particular specifications of the wind price dependence structure in the usual case of uncertain forward prices the optimal bidding strategy generally consists of a bid curve for wind power rather than a fixed quantity bid a discussion of the risk averse problem is also provided an analytical result is available for aversion to production volume risk however we doubt whether wind owners should be risk averse with respect to the income from a single settlement period given the large number of such periods in a year

power tac a competitive economic simulation of the smart grid sustainable energy systems of the future will need more than efficient clean low cost renewable energy sources they will also need efficient price signals that motivate sustainable energy consumption as well as a better real time alignment of energy demand and supply the power trading agent competition power tac is a rich competitive simulation of future retail power markets this simulation will help us to understand the dynamics of customer and retailer decision making and the robustness of market designs by stimulating researchers to develop broker agents and benchmark them against each other this will provide compelling actionable information for policymakers and industry leaders we describe the competition scenario in detail and we demonstrate behaviors that arise from the interaction of customer and broker models

modeling the impact of a wind power producer as a price maker wind energy is present in many countries throughout the world the main types of wind sales in electricity markets are via regulated tariffs or pool based markets production companies choose cost effective options for selling wind energy and some markets like the irish electricity market use regulated tariffs to remunerate wind production this paper aims to provide some answers to explain what effect wind offers may have in an electricity market if wind power producers participated in the day ahead market without receiving any premium or aid a price maker optimization model is used to detect its effect on prices the model encompasses energy offers by other technologies using residual demand curves and detailed modeling of wind imbalances it is observed that wind acting as price maker reduces electricity prices and the imbalance penalties help the system operator to reduce imbalances a realistic case study using data from the irish electricity market illustrates the methodology used comparing the effect of imbalance penalties in the models in terms of profit and total imbalance of the system

belief based equilibria in the repeated prisoners dilemma with private monitoring abstract we analyze repeated prisoners dilemma games with imperfect private monitoring and construct mixed trigger strategy equilibria such strategies have a simple representation where a player s action only depends upon her belief that her opponent s are continuing to cooperate when monitoring is almost perfect the symmetric efficient outcome can be approximated in any prisoners dilemma game while every individually rational feasible payoff can be approximated in a class of such games the efficiency result extends when there are more than two players it requires that monitoring be sufficiently accurate but does not require very low discounting when a public randomization device is available journal of economic literature classification numbers c73 d82

efficiency in repeated prisoner s dilemma with private monitoring abstract this paper analyzes repeated games with private monitoring where in each period each player receives a signal of the other player s action in the previous period and that signal is private information previous literature on discounted repeated games with private monitoring has not shown whether or not nearly efficient equilibria exist for a repeated prisoner s dilemma satisfying a certain assumption regarding stage game payoffs we show that there exists a nearly efficient sequential equilibrium provided that imperfectness of signals is small and players are patient journal of economic literature classification number c73