Information aggregation in experimental asset markets in the presence of a manipulator

We study with the help of a laboratory experiment the conditions under which an uninformed manipulator—a robot trader that unconditionally buys several shares of a common value asset in the beginning of a trading period and unwinds this position later on—is able to induce higher asset prices. We find that the average price is significantly higher in the presence of the manipulator if and only if the asset takes the lowest possible value and insiders receive perfect information about the true value of the asset. It is also evidenced that the robot trader makes trading gains. Finally, both uninformed and partially informed traders may suffer from the presence of the robot.     

The impact of instructions and procedure on reducing confusion and bubbles in experimental asset markets

In 1988 Smith, Suchanek, and Williams (henceforth SSW) introduced a very influential model to test the efficiency of experimental asset markets. They and many subsequent studies observe that bubbles are robust to many treatment changes. Instead, bubbles are avoided only when subjects are experienced in the same setting, when the dividend-process is experienced by subjects beforehand, or when the fundamental value-process (FV) is presented in a well understandable context to reduce subjects’ confusion. We extend this line of research and show that even marginal changes in the experimental instructions/procedure can eliminate bubbles in the SSW-model. In particular, we show that mispricing is significantly reduced and overvaluation is eliminated completely (i) when the fundamental value process is displayed in a graph instead of a table or (ii) when subjects are asked about the current fundamental value at the beginning of each period. From a questionnaire conducted at the end of the experiment we infer that these treatment changes help to improve subjects’ understanding of the FV-process. We conclude that all bubble reducing factors have one common feature: they allow subjects to understand the non-intuitive declining FV-process of the SSW-model better and thus reduce subjects’ confusion about the FV-process.     

Dividend timing and behavior in laboratory asset markets

Summary. This paper investigates the effect of dividend timing on price bubbles and endogenous expectations in twenty-six laboratory asset markets. In ten "A1" markets, a single dividend is paid at the end of the trading horizon. In nine "A2" markets, dividends are paid at the end of each trading period. In seven "A3" markets, some of the dividends are paid at the end of the trading horizon, and the rest are paid on a per-period basis. The results indicate that price bubbles are most likely in A2 markets, less likely in A3 markets, and least likely in A1 markets. Six distinct hypotheses are considered. The data suggest that the concentration of dividend value at a single point in time helps to create common expectations, and thus significantly reduce the incidence of bubbles. Also, the results underscore the difficulty facing econometric tests on field data where fundamental value has to be approximated.     

Endogenous trading constraints with incomplete asset markets

This paper endogenizes the borrowing constraints on capital in a production economy with incomplete markets. We find that these limits get looser with income, a property that is consistent with US data on credit limits. The framework with endogenous limits is then used to study the effects of a revenue neutral tax reform that eliminates capital income taxes. Our results illustrate that it is very important to take into account the effects of tax policies on the limits. Throughout the transition, these effects can be big enough to change the overall conclusion about the desirability of a tax reform.     

Exact arbitrage and portfolio analysis in large asset markets

Summary. We provide a detailed portfolio analysis for a financial market with an atomless continuum of assets. In the context of an exact arbitrage pricing theory (EAPT), we go beyond the characterization of the existence of important portfolios (normalized riskless, mean, cost, factor and mean-variance efficient portfolios) to furnish exact portfolio compositions in terms of explicit portfolio weights. Such an analysis has not been furnished before in the context of the asymptotic arbitrage pricing theory (APT). We also characterize conditions under which a mean-variance efficient portfolio is a benchmark portfolio used in the EAPT to proxy essential risk. We illustrate our results with several examples of specific financial markets. Received: May 30, 2002; revised version: August 15, 2002 RID="*" ID="*"Some of the results reported here constituted part of Cowles Foundation Discussion Paper– No. 1139 circulated under the title “Hyperfinite Asset Pricing Theory”; additional results were obtained when Sun visited the Department of Economics at Johns Hopkins University during March 2002. This paper was presented at the Conference on Economic Design held at NYU on July 6–9, 2002 Correspondence to: M. A. Khan     

Search and endogenous concentration of liquidity in asset markets

We develop a search-based model of asset trading, in which investors of different horizons can invest in two assets with identical payoffs. The asset markets are partially segmented: buyers can search for only one asset, but can decide which one. We show the existence of a “clientele’’ equilibrium where all short-horizon investors search for the same asset. This asset has more buyers and sellers, lower search times, and trades at a higher price relative to its identical-payoff counterpart. The clientele equilibrium dominates the one where all investor types split equally across assets, implying that the concentration of liquidity is socially desirable.     

International asset markets and real exchange rate volatility

The real exchange rate is very volatile relative to major macroeconomic aggregates and its correlation with the ratio of domestic over foreign consumption is negative (Backus–Smith puzzle). These two observations constitute a puzzle to standard international macroeconomic theory. This paper develops a two country model with complete asset markets and limited enforcement for international financial contracts that provides a possible explanation of these two puzzles. The model performs better than a standard incomplete markets model with a single non-contingent bond unless very tight borrowing constraints are imposed in the latter. With limited enforcement for both domestic and international financial contracts, the model's asset pricing implications are brought into line with the empirical evidence, albeit at the expense of raising real exchange rate volatility.     

Exact arbitrage, well-diversified portfolios and asset pricing in large markets

For a market with an atomless continuum of assets, we formulate the intuitive idea of a “well-diversified” portfolio, and present a notion of “exact arbitrage”, strictly weaker than the more conventional notion of “asymptotic arbitrage”, and necessary and sufficient for the validity of an APT pricing formula. Our formula involves “essential” risk, one based on a specific index portfolio constructed from factors and factor loadings that are endogenously extracted to satisfy an optimality property involving a finite number of factors. We illustrate how our results can be translated to markets with a large but finite number of assets.     

Price manipulation in an experimental asset market

We analyze in the laboratory whether an uninformed trader is able to manipulate the price of a financial asset by comparing the results of two experimental treatments. In the benchmark treatment, 12 subjects trade a common value asset that takes either a high or a low value. Only three subjects know the actual value of the asset while the market is open for trading. The manipulation treatment is identical to the benchmark treatment apart from the fact that we introduce a computer program as an additional uninformed trader. This robot buys a fixed number of shares in the beginning of a trading period and sells them again afterwards. Our main result shows that the last contract price is significantly higher in the manipulation treatment if the asset takes a low value and that private information is very well disseminated by both markets if the value of the asset is high. Finally, even though this simple manipulation program loses money on average, it is profitable in some instances.     

Strategy-proofness in experimental matching markets

We introduce two novel matching mechanisms, Reverse Top Trading Cycles (RTTC) and Reverse Deferred Acceptance (RDA), with the purpose of challenging the idea that the theoretical property of strategy-proofness induces high rates of truth-telling in economic experiments. RTTC and RDA are identical to the celebrated Top Trading Cycles (TTC) and Deferred Acceptance (DA) mechanisms, respectively, in all their theoretical properties except that their dominant-strategy equilibrium is to report one’s preferences in the order opposite to the way they were induced. With the focal truth-telling strategy being out of equilibrium, we are able to perform a clear measurement of how much of the truth-telling reported for strategy-proof mechanisms is compatible with rational behaviour and how much of it is caused by confused decision-makers following a default, focal strategy without understanding the structure of the game. In a school-allocation setting, we find that roughly half of the observed truth-telling under TTC and DA is the result of naïve (non-strategic) behaviour. Only 14–31% of the participants choose actions in RTTC and RDA that are compatible with rational behaviour. Furthermore, by looking at the responses of those seemingly rational participants in control tasks, it becomes clear that most lack a basic understanding of the incentives of the game. We argue that the use of a default option, confusion and other behavioural biases account for the vast majority of truthful play in both TTC and DA in laboratory experiments.

     

On the welfare equivalence of asset markets and banking in Diamond Dybvig economies

Why do people choose bank deposit contracts over a direct participation in asset markets? In their seminal paper, Diamond and Dybvig’s (1983) answer this question by claiming that bank deposit contracts can implement allocations that are welfare superior to asset markets equilibria. The present paper demonstrates that this claim is false whenever the asset market participants are highly rational.     

Sick pay provision in experimental labor markets

Sick pay is a common provision in most labor contracts. This paper employs an experimental gift exchange environment to explore two related questions using both managers and undergraduates as subjects. First, do workers reciprocate generous sick pay with higher effort? Second, do firms benefit from offering sick pay? Our main finding is that workers do reciprocate generous sick pay with higher effort. However, firms benefit from offering sick pay in terms of profits only if there is competition among firms for workers. Consequently, competition leads to a higher voluntary provision of sick pay relative to a monopsonistic labor market.     

The set of sunspot equilibria in economies with incomplete financial markets: variable asset prices

Summary. I consider the set of equilibria of two-period economies with S extrinsic states of nature in the second period and I assets with linearly independent nominal payoffs. Asset prices are variable. If the number of agents is greater than (S-I), the payoff matrix is in general position and S 2I, the set of equilibrium allocations generically (in utility function space) contains a smooth manifold of dimension (S-1). Moreover, the map from states o f nature to equilibrium allocations (restricted to this manifold) is one-to-one at each equilibrium. Received: February 23, 1998; revised version: June 1, 2000     

Price flexibility and market performance in experimental markets

Summary Posted offer and double auction pricing institutions are examples of fixed and flexible pricing institutions, respectively. In laboratory settings, double auction markets dominate posted offer institutions in terms of the amount of potential surplus which traders are able to extract. These results are invariant with respect to the experience of traders or the perishability of the good traded. Performance differences across institutions may be due to information differences. The introduction of a second price-posting in the posted offer institution results in a pricing institution which is closer to the double auction's flexible pricing environment. Laboratory results suggest that under otherwise comparable conditions, this innovation is sufficient to remove the performance differences which have been demonstrated to exist between the posted offer and double auction institutions.We acknowledge the support of the Social Sciences and Humanities Research Council of Canada and the Arts Research Board of McMaster University. We thank Robert Moir and Susan Sabourin for computational work on this project and the fifteen undergraduates who worked as recorders and recruiters. We also thank Charles Plott and seminar participants at the Economic Science Association, Canadian Economics Association, and Waterloo University for the comments received on recent versions of this work.     

Aggregation of heterogenous beliefs,asset pricing,and risk sharing in complete financial markets

Given a competitive equilibrium in complete asset markets, we propose a method that aggregates heterogeneous individual beliefs into a single “market probability,” which, if commonly shared by investors, generates the same marginal valuation of assets by the market as well as by each individual investor. As a result of the aggregation process, the market portfolio may have to be scalarly adjusted, upward or downward, a reflection of an aggregation bias due to the diversity of beliefs. From a dual viewpoint, the standard construction of an expected utility-maximizing aggregate investor designed to represent the economy in equilibrium, is shown to be also valid in the case of heterogeneous beliefs, modulo the above scalar adjustment of the market portfolio, thereby generating an Adjusted version of the Consumption based Capital Asset Pricing Model (ACCAPM). We analyze how the allocation of aggregate and individual risks relates to deviations of individual beliefs from the aggregate market probability. Finally, we identify the channels through which the distribution of beliefs and other microeconomic characteristics (incomes, attitudes toward risk) across investors impact the pricing of risky assets an may contribute to explaining the equity premium puzzle.     

Limited asset markets participation, monetary policy and (inverted) aggregate demand logic

This paper incorporates limited asset markets participation in dynamic general equilibrium and develops a simple analytical framework for monetary policy analysis. Aggregate dynamics and stability properties of an otherwise standard business cycle model depend nonlinearly on the degree of asset market participation. While ‘moderate’ participation rates strengthen the role of monetary policy, low enough participation causes an inversion of results dictated by conventional wisdom. The slope of the ‘IS’ curve changes sign, the ‘Taylor principle’ is inverted, optimal welfare-maximizing discretionary monetary policy requires a passive policy rule and the effects and propagation of shocks are changed. However, a targeting rule implementing optimal policy under commitment delivers equilibrium determinacy regardless of the degree of asset market participation. Our results may justify Fed's behavior during the ‘Great Inflation’ period.     

Trade policy with asset markets: The role of financial structure for time consistency

The present study uses a two-country, two-good, stochastic general equilibrium trade model to analyze the implications of optimal trade policy under uncertainty in the presence of financial markets. Using such a framework, I demonstrate that the policy-active home government, acting to maximize domestic welfare, will always have incentive to revise the previously announced import tariff policy once an asset position is taken by the representative agent in each country engaged in trade. The resulting time-consistent solution will be sensitive to the composition of asset income. Since the fiancial contracts can be combined in an infinite number of ways to yield the same optimal level of asset income, there will exist multiple time-consistent solutions, one for each financial structure. Using a specific log utility function, I also show that for certain financial structures, precommitment solutions will be replicated by time-consistent solutions, a result which marks a significant departure from the standard deterministic framework.