on the effects of joint bidding in independent private value auctions an experimental study abstract this article explores the effect of a subset of symmetric bidders joining to bid together possible applications include mergers collusion and joint bidding arrangements the change produces a strong party with a more advantageous value distribution than the remaining weak bidder s the predicted effects include inefficiency a decrease in the seller s revenue and higher bidders payoffs under risk neutrality the members of the strong party benefit less than the weak bidders the prediction is reversed when the bidders are sufficiently risk averse these hypotheses are tested experimentally contrary to the theory joint bidding increases efficiency and the seller s revenue decreases by less than expected strong bidders benefit more than weak bidders indicating that incentives to bid jointly may be greater than hypothesized additionally the experiment assesses the effect of group decision making a nash equilibrium prediction for individual group differences based on differences in risk attitudes is not supported by the data

multiple round timber auction design and simulation this paper presents a multiple round timber auction simulation developed in order to study various configurations of auction design in this study simultaneous sequential timber auctions are modelled and analysed using agent based simulation technology as there are many individual items in the auction to be sold the auction designer defines several rounds that are sequential at pre defined intervals at each round the auction designer announces several simultaneous auctions since bidders are offered different items at each round a mathematical linear programing model for selecting the best set of items to bid for is presented different bidding patterns are simulated and compared in various setup configurations the most advanced of these strategies are adaptive and use agent learning capability the comparisons include the success rate of winning the auction and the winning price per m3 this study suggests an efficient bidding pattern for bidders to bid in order to achieve to their goal and increase their profit similarly in order to increase profit the auctioneer i e the government needs to control several auction parameters including the number of auctions per year the lot size the auction periodicity and the number of bidders this study also suggests parameters configurations that to maximise revenue for the auctioneer

limited rationality and strategic interaction the impact of the strategic environment on nominal inertia much evidence suggests that people are heterogeneous with regard to their abilities to make rational forward looking decisions this raises the question as to when the rational types are decisive for aggregate outcomes and when the boundedly rational types shape aggregate results we examine this question in the context of a long standing and important economic problem the adjustment of nominal prices after an anticipated monetary shock our experiments suggest that two types of bounded rationality money illusion and anchoring are important behavioral forces behind nominal inertia however depending on the strategic environment bounded rationality has vastly different effects on aggregate price adjustment if agents actions are strategic substitutes adjustment to the new equilibrium is extremely quick whereas under strategic complementarity adjustment is both very slow and associated with relatively large real effects this adjustment difference is driven by price expectations which are very flexible and forward looking under substitutability but adaptive and sticky under complementarity moreover subjects expectations are also considerably more rational under substitutability

technical and economic performance of residential solar water heating in the united states abstract this paper examines the regional technical and economic performance of residential rooftop solar water heating swh technology in the u s it focuses on the application of swh to consumers in the u s currently using electricity for water heating which currently uses over 120 billion kwh per year the variation in electrical energy savings due to water heating use inlet water temperature and solar resource is estimated and applied to determine the regional break even cost of swh where the life cycle cost of swh is equal the life cycle energy savings for a typical residential consumer a swh system will reduce water heating energy demand by 50 85 or a savings of 1600 2600 kwh per year for the largest 1000 electric utilities serving residential customers in the united states as of 2008 this corresponds to an annual electric bill savings range of about 100 to over 300 reflecting the large range in residential electricity prices this range in electricity prices along with a variety of incentives programs corresponds to a break even cost of swh in the united states varying by more than a factor of five from less than 2250 system to over 10 000 system excluding hawaii and alaska despite a much smaller variation in the amount of energy saved by the systems a factor of approximately one and a half we also consider the relationships between collector area and technical performance swh price and solar fraction percent of daily energy requirements supplied by the swh system and examine the key drivers behind break even costs

the hayek hypothesis and long run competitive equilibrium an experimental investigation we report on an experiment investigating whether the hayak hypothesis smith 1982 extends to the long run setting we consider two environments one with a common production technology having a u shaped long run average cost curve and a single competitive equilibrium and another with a common constant returns to scale technology having a constant long run average cost curve and multiple competitive equilibria while there is convergence in both environments to the long run equilibrium it takes longer and is less robust than usually observed in the short run setting we show that price formation is adaptive and quickly converges to realized short run equilibrium but long run investment decisions exhibit very limited rationality we present and estimate an investment choice model that shows that only minimal rationality coupled with repeated decisions is enough to achieve high long run allocative eciency when markets use continuous double auctions jel classication c92 d02

co learning patterns as emergent market phenomena an electricity market illustration abstract the definition of emergence remains problematic particularly for systems with purposeful human interactions this study explores the practical import of this concept within a specific market context namely a double auction market for wholesale electric power that operates over a transmission grid with spatially located buyers and sellers each profit seeking seller is a learning agent that attempts to adjust its daily supply offers to its best advantage the sellers are co learners in the sense that their supply offer adjustments are in response to past market outcomes that reflect the past supply offer choices of all sellers attention is focused on the emergence of co learning patterns that is global market patterns that arise and persist over time as a result of seller co learning examples of co learning patterns include correlated seller supply offer behaviors and correlated seller net earnings outcomes heat maps are used to display and interpret co learning pattern findings one key finding is that co learning strongly matters in this auction market environment sellers that behave as gode sunder budget constrained zero intelligence agents randomly selecting their supply offers subject only to a break even constraint tend to realize substantially lower net earnings than sellers that tacitly co learn to correlate their supply offers for market power advantages

fairness price stickiness and history dependence in decentralized trade this chapter investigates the implications that social preferences have for the stationary strategic equilibrium of such a decentralized market agents are supposed to be averse to unfairly unfavorable as well as unfairly favorable deals in the spirit of fehr and schmidt 1999 but we stay rather close to standard individualistic preferences the negative weights on advantageous and disadvantageous deviations from what is considered as the fair benchmark are such that utility remains strictly increasing in own surplus share and in contrast to the original fehr schmidt model the fair split need not automatically be a 50 50 division any price between sellers cost and buyers willingness to pay may be the one which for whatever reasons is agents reference point in a given market this makes it possible to consider a more flexible notion of fairness than is usually done it is in line with cognitive dissonance theory from psychology and the noteworthy experiments of binmore et al 1991 1993 where subjects who were triggered to play different bargaining equilibria ended up considering very different surplus distributions as fair

an interdisciplinary model for macroeconomics macroeconomic modelling has been under intense scrutiny since the great financial crisis when serious shortcomings were exposed in the methodology used to understand the economy as a whole criticism has been levelled at the assumptions employed in the dominant models particularly that economic agents are homogeneous and optimizing and that the economy is equilibrating this paper seeks to explore an interdisciplinary approach to macroeconomic modelling with techniques drawn from other natural and social sciences specifically it discusses agent based modelling which is used across a wide range of disciplines as an example of such a technique agent based models are complementary to existing approaches and are suited to answering macroeconomic questions where complexity heterogeneity networks and heuristics play an important role

capture and ideology in the economic theory of politics the economic theory of regulation long ago put public interest theories of politics to rest these theories have correctly been viewed as normative wishings rather than explanations of real world phenomena they have been replaced by models of political behavior that are consistent with the rest of microeconomics anthony downs 1957 james buchanan and gordon tullock 1965 george stigler 1971 sam peltzman 1976 recently however debate has arisen over whether some version of a public interest theory of regulation will have to be readmitted to our thinking about actions and results in the political arena what is at issue is the empirical importance of the altruistic publicly interested goals of rational actors in determining legislative and regulatory outcomes james kau and paul rubin 1979 kalt 1981 peltzman 1982 this study assesses the nature and significance of publicly interested objectives in a particular instance of economic policymaking u s senate voting on coal strip mining regulations the existence of such objectives is of course no contradiction of the economic view of human behavior kenneth arrow 1972 gary becker 1974 and may well be rooted in genetic biological history becker 1976 jack hirshleifer 1978 generally however individuals altruistic publicly interested goals have been given little attention this reflects the judgment that such goals are so empirically unimportant as to allow the use of occam s razor in positive models or well founded apprehensions that these goals are unusually difficult to identify measure and analyze notwithstanding the latter problem we find that approaches which confine themselves to a view of political actors as narrowly egocentric maximizers explain and predict legislative outcomes poorly the tracking and dissecting of the determinants of voting on coal strip mining policy suggest that the economic theory of politics has been prematurely closed to a broader conception of political behavior

learning to deal with repeated shocks under strategic complementarity an experiment experimental evidence shows that the rational expectations hypothesis fails to characterize the path to equilibrium after an exogenous shock when actions are strategic complements under identical shocks however repetition allows adaptive learning so that inertia in adjustment should fade away with experience if this finding proves to be robust inertia in adjustment may be irrelevant among experienced agents the conjecture in the literature is that inertia would still persist perhaps indefinitely in the presence of real world complications such as nonidentical shocks herein we empirically test the conjecture that the inertia in adjustment is more persistent if the shocks are nonidentical for both identical and nonidentical shocks we find persistent inertia and similar patterns of adjustment that can be explained by backward looking expectation rules a reformulation of naive expectations with similarity based learning approach is found to have a higher predictive power than rational and trend following rules

do institutions promote rationality an experimental study of the three door anomaly the three door problem is an example of a systematic violation of a key rationality postulate that has attracted much attention in this seemingly simple individual decision task most people initially fail to apply correctly bayes law and to make the payoff maximizing choice previous experimental studies have shown that individual learning reduces the incidence of irrational choices somewhat but is far from eliminating it we experimentally study the roles of communication and competition as institutions to mitigate the choice anomaly we show that the three door anomaly can be entirely eliminated by these institutions

learning to bid the design of auctions under uncertainty and adaptation we examine auction design in a context where symmetrically informed adaptive agents with common valuations learn to bid for a good despite the absence of private valuations asymmetric information or risk aversion bidder strategies do not converge to the bertrand nash equilibrium strategies even in the long run deviations from equilibrium strategies depend on uncertainty regarding the value of the good auction structure the agents learning model and the number of bidders although individual agents learn nash bidding strategies in isolation the learning of each agent by flattening the best reply correspondence of other agents blocks common learning these negative externalities are more severe in second price auctions auctions with many bidders and auctions where the good has an uncertain value ex post

a rule of one a rule ofone one rational person is enough to make a market one irrational person is enough to break a game let me explain the power of the market as an exchange institution rests in its ability to move resources from lowto highvalued uses the market works if one person is rational enough to look for arbitrage opportunities among the other irrational players he buys low and sells high the market collects and disseminates this information such that others

circulation versus advertiser appeal in the newspaper industry an empirical investigation advertising space is not a homogeneous commodity but something whose value depends on the characteristics of a newspaper s readership it is suggested in particular that the proportion of readers belonging to the more affluent social categories will exert a strong positive influence on advertising this paper investigates the circulation readership profile relation using a simple simultaneous equation framework the model is then estimated across a sample of british and irish daily and sunday newspapers using data collected from industry sources the paper then seeks to quantify the trade off between circulation and the proportion of high income readers copyright 1989 by blackwell publishing ltd

market simulation and the provision of public goods a non paternalistic response to anomalies in environmental evaluation most normative economics assumes that individuals have coherent preferences this paper responds to growing evidence of failures of this assumption particularly in the context of stated preference methods widely used in environmental policy analysis it proposes a non paternalistic concept of consumer sovereignty that does not assume preference coherence is satisfied by competitive markets and can be applied to the provision of public goods a key implication is that decisions should reflect valuations revealed at the point of consumption such valuations which can be inferred from hedonic prices may be less susceptible to willingness to accept wta willingness to pay wtp disparities than those elicited by stated preference methods

price formation in single call markets this paper reports a laboratory experiment designed to examine the price formation process in a simple market institution the single call market the experiment features random values and costs each period so each period generates a new price formation observation other design features are intended to enhance the predictive power of the bayesian nash equilibrium bne theory developed recently for this trading institution we find that the data support several qualitative implications of the bne but that subjects bid and ask behavior is not as responsive to changes in the pricing rule as the bne predictions bids and asks tend to reveal more of the underlying values and costs than predicted particularly when subjects are experienced nevertheless observed trading efficiency falls below the bne prediction the results offer more support for the bne when subjects compete against nash robot opponents a simple learning model accounts for several of the deviations from bne

markups in double auction markets abstract we study the continuous double auction cda market with simulated traders using three simple markup rules relative to analytic results obtained for markups in the simpler call market cm we find that uniform cda markups have a more complex and non monotonic impact on cda market outcomes such as price volume and efficiency the symmetric nash equilibrium markup in the cda is remarkably close to the most efficient markup in thick markets which may partially explain the mysterious efficiency for cda market

bounded rationality and the emergence of simplicity amidst complexity abstract the purpose of this essay is to explore the relationship between the simple and the complex in economics by anchoring our analysis on bounded rationality much of the conventional literature focuses on un bounded rationality of the rationality as consistency variety theorizing of bounded rationality tends to assume that the problem to be solved is independent of the nature of bounded rationality following the insights from the works of herbert simon and contributions from outside economics both bounded rationality and the environment are inextricably linked the boundaries between bounded rationality and its environment can shift the form in which bounded rationality is found depends on the complexity of the environment furthermore if local interactions between bounded rational agents result in the formation of hierarchies the complexity of the collective system will change whether this will occur depends on the nature of bounded rationality at the individual level

allocation of track capacity experimental evidence on the use of priority auctioning in the railway industry allocation of track capacity concerns multiple users facing demand indivisibilities running trains over an inelastic supply of railway tracks the paper suggests a vickrey type mechanism to handle incentive aspects of this technically complex optimisation task here the price for operating a train will correspond to the bids foregone by other operators who are pushed off their preferred routes the paper reports the results of 11 experimental markets using variations of this mechanism where each market includes up to 10 trading periods and subjects bid for routes over a highly stylised railway network the experiments generated solutions that capture 90 100 of potential benefits

price formation in double auctions abstract we develop a model of information processing and strategy choice for participants in a double auction sellers in this model form beliefs that an offer will be accepted by some buyer similarly buyers form beliefs that a bid will be accepted these beliefs are formed on the basis of observed market data including frequencies of asks bids accepted asks and accepted bids then traders choose an action that maximizes their own expected surplus the trading activity resulting from these beliefs and strategies is sufficient to achieve transaction prices at competitive equilibrium and complete market efficiency after several periods of trading journal of economic literatureclassification numbers d41 d44 d8

comovement or safe haven the effect of corruption on the market risk of sovereign bonds of emerging economies during financial crises in this study i explore the role of corruption in the cross market time varying linkage between sovereign bonds of emerging markets and the us stock market it shows that corruption plays a prominent role in the behaviour of capm beta under different market conditions the sensitivity of sovereign bonds issued by countries perceived as more corrupt to systematic shocks increases during financial crises the prices of bonds issued by less corrupt countries are determined more idiosyncratically under extreme market conditions and realize more hedging benefits against s p 500 risk to explain these findings i integrate results from behavioural finance i propose a comovement model built on barberis et al 2005 where investors load more worldwide news on sovereign bonds issued by more corrupt countries when their sentiment deteriorates

economists models of learning abstract economic theorists have intensively studied learning in games and decisions over the last decade this essay puts some of the work in perspective and offers opinions about what still needs to be learned journal of economic literature classification numbers c73 d83

market theories evolve and so do markets responding to mirowski s target article this paper discusses some intellectual currents of the 1970s to 1990s and offers suggestions on measuring market performance on including automated agents as market participants on evolving new market formats and on dealing with highly differentiated goods acknowledgments i am grateful to associate editor rosser for inviting me to participate in this symposium and to philip mirowski for writing a timely and engaging target article some of the material comes from a recent nsf proposal co written with james c cox the paper mentions many other intellectual debts of course i retain sole responsibility for lapses of style and substance

the complexity of exchange the computational complexity of two classes of market mechanisms is compared first the walrasian interpretation in which prices are centrally computed by an auctioneer recent results on the computational complexity are reviewed the non polynomial complexity of these algorithms makes walrasian general equilibrium an implausible conception second a decentralised picture of market processes is described involving concurrent exchange within transient coalitions of agents these processes feature price dispersion yield allocations that are not in the core modify the distribution of wealth are always stable but path dependent replacing the walrasian framing of markets requires substantial revision of conventional wisdom concerning markets

is the media liberal an indirect test using news magazine circulation many critics allege that the us national news media is biased in favour of liberal causes and democratic candidates the lack of an objective measure of news content ensures that such charges remain controversial i consider an indirect test for media bias if the national news media do exhibit a liberal bias consumption should be higher in liberal media markets ceteris paribus i examine determinants of circulation of the three major weekly news magazines across the us and find that newsweek and time have higher circulation in liberal markets while us news has higher circulation in conservative markets the evidence is consistent with a liberal bias for time and newsweek while us news may be relatively conservative but still left of centre or absolutely conservative

examining the effectiveness of price limits in an artificial stock market abstract this paper proposes an agent based framework to examine the effectiveness of price limits in an artificial stock market the market is composed of many boundedly rational and heterogeneous traders whose learning behavior is represented by a genetic programming algorithm we calibrate the model to replicate several stylized facts observed in real financial markets based on this environment the impacts of price limits are analyzed from the perspectives of volatility price distortion volume and welfare we find that the imposition of price limits possesses both positive and negative effects however compared with the market without price limits appropriate price limits help to reduce volatility and price distortion and increase the liquidity and welfare

redistribution and market efficiency an experimental study abstract we study the interaction between competitive markets and income redistribution that reallocates unequal pre tax market incomes away from the rich to the poor majority in one setup participants earn their income by trading in a double auction da with exogenous zero or full redistribution in another setup after trading they vote on redistributive tax policies in a majoritarian election with two competing candidates this results in virtually full redistribution even when participants have the opportunity to influence taxes by transferring money to the candidates we find that the high redistribution reduces trading efficiency but not as much as predicted if market participants trade randomly this is because rather than capitulating to the much lower trading incentives many participants respond to redistribution by asking and bidding more conservatively in the da and in this way help to prevent further efficiency losses

a test of the modigliani miller invariance theorem and arbitrage in experimental asset markets modigliani and miller show that the total market value of a firm is unaffected by a repackaging of asset return streams to equity and debt if pricing is arbitrage free we investigate this invariance theorem in experimental asset markets finding value invariance for assets of identical risks when returns are perfectly correlated however exploiting price discrepancies has risk when returns have the same expected value but are uncorrelated in which case the law of one price is violated discrepancies shrink in consecutive markets but persist even with experienced traders in markets where overall trader acuity is high assets trade closer to parity

allocative efficiency of markets with zero intelligence traders market as a partial substitute for individual rationality we report market experiments in which human traders are replaced by zero intelligence programs that submit random bids and offers imposing a budget constraint i e not permitting traders to sell below their costs or buy above their values is sufficient to raise the allocative efficiency of these auctions close to 100 percent allocative efficiency of a double auction derives largely from its structure independent of traders motivation intelligence or learning adam smith s invisible hand may be more powerful than some may have thought it can generate aggregate rationality not only from individual rationality but also from individual irrationality

avoidable cost ride a double auction roller coaster the double auction trading institution has been highly efficient across diverse marginal cost market structures whether human subjects or zero intelligence robots populated those markets accordingly many researchers suspect that double auction performance transcends market structure and agent strategy but the authors show that large avoidable costs undermine the efficiency and stability of human subject double auctions and these low human efficiencies are simultaneously well above zero intelligence efficiencies their results dramatically illustrate the potential havoc wrought by highly competitive institutions when they must cope with nonconvex technologies copyright 1996 by american economic association

the approach of institutional economics this paper assesses the old institutional economics it emphasizes the importance of key old institutionalist themes concerning the necessity of habits and rules and the role of institutions a problem in the alternative theoretical program of the new institutionalism is the untenability of its assumption of an original institution free market or state of nature even optimizing behavior requires the prior existence of habits and rules although it still lacks a complete and systematic theory the evolutionary approach of the old institutionalists tackles the problem of the interactive relationship of actor to structure without analytical reduction to one or the other

consumer inertia choice dependence and learning from experience in a repeated decision problem abstract understanding when and how individuals think about real life problems is a central question in economics this paper studies the role of inertia inattention state dependence and learning the empirical setting is a tariff experiment when optional measured tariffs for local telephone calls were introduced unanticipatedly we find that consumers tend to align their choices of tariff and telephone use levels correctly despite low potential savings mistakes are not permanent as individuals actively engage in tariff switching in order to reduce the monthly cost of telephone service ignoring unobservable heterogeneity and the endogeneity of past choices would have reversed these results

follies subdued informational efficiency under adaptive expectations and confirmatory bias abstract we study the informational efficiency of a market with a single traded asset the price initially differs from the fundamental value about which the agents have noisy private information which is on average correct a fraction of traders revise their price expectations in each period the price at which the asset is traded is public information the agents expectations have an adaptive component and a social interactions component with confirmatory bias we show that taken separately each of the deviations from rationality worsens the informational efficiency of the market however when the two biases are combined the degree of informational inefficiency of the market measured as the deviation of the long run market price from the fundamental value of the asset can be non monotonic both in the weight of the adaptive component and in the degree of confirmatory bias for some ranges of parameters two biases tend to mitigate each other s effect thus increasing informational efficiency

tradable deficit permits efficient implementation of the stability pact in the european monetary union tradable deficit permits efficient implementation of the stability pact borrowing from the experience of environmental markets this paper proposes a system of tradable deficit permits as an efficient mechanism for implementing fiscal constraints in the european monetary union having chosen an aggregate target for the union and an initial distribution of permits emu countries could be allowed to trade rights to deficit creation the scheme exploits countries incentives to minimize their costs is transparent and flexible in accommodating idiosyncratic shocks and allows for adjustments in case of europe wide recessions in addition it need not treat all countries identically and can be designed to penalize countries with higher debt to gdp ratios finally the scheme rewards countries for reducing their deficit below the initial allowance lending credibility to the stability pact s goal of a balanced budget in the medium run alessandra casella

three minimal market institutions with human and algorithmic agents theory and experimental evidence we define and examine the performance of three minimal strategic market games sell all buy sell and double auction in laboratory relative to the predictions of theory unlike open or partial equilibrium settings of most other experiments these closed exchange economies have limited amounts of cash to facilitate transactions and include feedback general equilibrium theory since it abstracts away from market mechanisms and has no role for money or credit makes no predictions about how the paths of convergence to the competitive equilibrium may differ across alternative mechanisms

the liberal media bias or customer preferences allegations of liberal bias against the national news media in the us remain very contentious conservative critics of the media argue biased news stems from liberal leaning journalists another explanation of alleged bias could be that liberals have a greater demand for news than moderates or conservatives so the media simply tailors its product to their customers i test whether liberals in the us have a greater demand for news by investigating the determinants of newspaper circulation across states and metropolitan areas i find mixed evidence for liberal demand circulation is higher in more liberal metropolitan areas but is independent of local political preferences across states

voting for pareto optimality a multidimensional analysis we compare unanimity rule and majority rule in their abilities to produce pareto superior and pareto optimal alternatives in fixed number of rounds of voting using a two dimensional spatial voting model with random proposals sincere proposals and strategic proposals our findings show that for random or sincere proposals majority rule is at least as likely to select a pareto optimal outcome as unanimity rule for strategic proposals the subgame perfect equilibrium under unanimity rule is pareto optimal for other k majority rules the outcome is pareto optimal or very close to it for outcomes that are both pareto optimal and pareto superior unanimity rule outperforms majority rule

on the robustness of non linear personalized price combinatorial auctions abstract though the vcg auction assumes a central place in the mechanism design literature there are a number of reasons for favoring iterative combinatorial auctions icas several promising ica formats were developed based on primal dual and subgradient algorithms prices are interpreted as a feasible dual solution and the provisional allocation is interpreted as a feasible primal solution ibundle 3 dvsv and ascending proxy auction result in vcg payoffs when the coalitional value function satisfies buyer submodularity and bidders bid straightforward which is an ex post nash equilibrium in this case ibea and creditdebit auctions do not even require the buyer submodularity and achieve the same properties for general valuations often however one cannot assume straightforward bidding and it is not clear from the theory how these non linear personalized price auctions nlppas perform in this case robustness of auctions with respect to different bidding behavior is a critical issue for any application we conducted a large number of computational experiments to analyze the performance of nlppas with respect to different bidding strategies and valuation models we compare nlppas with the vcg auction and with icas with linear prices such as alps and the combinatorial clock auction while nlppas performed very well in case of straightforward bidding we observe problems with revenue efficiency and speed of convergence when bidders deviate

market clearing and price formation abstract considered here is decentralized exchange of privately owned commodity bundles voluntary transactions take the form of repeated bilateral barters under broad and reasonable hypotheses the resulting process converges to competitive equilibrium price taking behavior is not assumed prices emerge over time they need neither be anticipated nor known at any interim stage

characterizing effective trading strategies insights from a computerized double auction tournament abstract this paper presents a comparative analysis of 30 computer trading programs that participated in a double auction tournament held at the santa fe institute in 1990 and 1991 our objective is to characterize the form of effective trading strategies in double auction markets we find that a simple rule of thumb is a highly effective and robust performer over a wide range of trading environments significantly outperforming more complex algorithms that use statistically based predictions of future transaction prices explicit optimizing principles and sophisticated learning algorithms