Competition in two‐sided markets

Many markets involve two groups of agents who interact via “platforms,“ where one group's benefit from joining a platform depends on the size of the other group that joins the platform. I present three models of such markets: a monopoly platform; a model of competing platforms where agents join a single platform; and a model of “competitive bottlenecks” where one group joins all platforms. The determinants of equilibrium prices are (i) the magnitude of the cross‐group externalities, (ii) whether fees are levied on a lump‐sum or per‐transaction basis, and (iii) whether agents join one platform or several platforms.     

Interviewing in two‐sided matching markets

We introduce the interview assignment problem, which generalizes classic one‐to‐one matching models by introducing a stage of costly information acquisition. Firms learn preferences over workers via costly interviews. Even if all firms and workers conduct the same number of interviews, realized unemployment depends also on the extent to which agents share common interviewing partners. We introduce the concept of overlap that captures this notion and prove that unemployment is minimized with perfect overlap: that is, if two firms interview any common worker, they interview the exact same set of workers.     

Pricing and commitment by two‐sided platforms

I study pricing and commitment by platforms in two‐sided markets with the following characteristics: (i) platforms are essential bottleneck inputs for buyers and sellers transacting with each other; (ii) sellers arrive before buyers; and (iii) platforms can charge both fixed fees and variable fees (royalties). I show that a monopoly platform may prefer not to commit to the price it will charge buyers at the same time it announces its seller price if it faces unfavorable seller expectations. With competing platforms, commitment makes the existence of an exclusive equilibrium (in which sellers register with only one platform) less likely, but it has no impact on multi‐homing equilibria (in which sellers support both platforms) whenever these exist.     

Two‐sided markets: a progress report

We provide a roadmap to the burgeoning literature on two‐sided markets and present new results. We identify two‐sided markets with markets in which the structure, and not only the level of prices charged by platforms, matters. The failure of the Coase theorem is necessary but not sufficient for two‐sidedness. We build a model integrating usage and membership externalities that unifies two hitherto disparate strands of the literature emphasizing either form of externality, and obtain new results on the mix of membership and usage charges when price setting or bargaining determine payments between end‐users.     

Preferred suppliers in auction markets

This article examines agreements between a buyer and one of the suppliers which increase their joint surplus. The provisions of such agreements depend on the buyer's ability to design the rules of the final procurement auction. When the buyer does not have this ability, their joint surplus can be increased by an agreement which grants to the preferred supplier a right of first refusal on the lowest price from the other suppliers. When the buyer has this ability, their joint surplus can be maximized by a revelation game for the cost of the preferred supplier and a reserve price based on that cost.     

Integrating auction and search markets: The slow Dutch auction

The issue of choosing to sell property by auction or by traditional negotiated search markets is addressed in this article. A general selling institution called the slow Dutch auction is introduced. This general selling mechanism reduces to either a conventional auction, a posted offer, or some time dependent mix of these selling institutions depending on the pricing rule chosen by the seller. We model search by having potential buyers whose private valuation for the property is unknown to the seller arrive randomly over time. With this general framework the seller's problem is to choose a selling mechanism that maximizes expected wealth. Surprisingly, we find that the optimal selling institution is always a posted offer market. The seller chooses an optimal posted price and waits until a buyer arrives who is willing to pay this price. Auctions are never optimal.     

Optimal design of derivatives in illiquid markets*

Abstract

The aim of this paper is to determine the optimal structure of derivatives written on an illiquid asset, such as a catastrophic or a weather event. This transaction involves two agents: a bank which wants to hedge its initial exposure towards this illiquid asset and an investor which may buy the contract. Both agents also have the opportunity to invest their residual wealth on a financial market.

Based on a utility maximization point of view, we determine an optimal profile (and its value) such that it maximizes the bank's utility given that the investor decides to make the deal only if it increases its utility. In the case of exponential utility, we show that the pricing rule is a non-linear function of the structure and that the bank always transfers the same proportion of its initial exposure. In the general case, an additional term appears, depending only on the relative log-likelihood of the two agents' views of the distribution of the illiquid asset.     

Insider trading in sequential auction markets with risk-aversion and time-discounting

We extend Kyle's [Kyle, A. S. 1985. “Continuous Auctions and Insider Trading.” Econometrica 53, 1315–1335] analysis of sequential auction markets to the case in which the insider is risk-averse and discounts her trading profits as her private information is long-lived. We see that time-discounting exacerbates the impact of risk-aversion on the optimal trading strategy of the insider. Ceteris paribus, a larger degree of risk-aversion or a smaller time-discount factor induces the informed agent to consume more rapidly her informational advantage increasing the liquidity and efficiency of the securities market.     

A simulation analysis of the microstructure of double auction markets

Abstract

We introduce an order-driven market model with heterogeneous agents trading via a central order matching mechanism. Traders set bids and asks and post market or limit orders according to exogenously fixed rules. We investigate how different trading strategies may affect the dynamics of price, bid-ask spreads, trading volume and volatility. We also analyse how some features of market design, such as tick size and order lifetime, affect market liquidity. The model is able to reproduce many of the complex phenomena observed in real stock markets.     

An optimal auction with identity‐dependent externalities

We analyze the problem of a seller of multiple identical units of a good who faces a set of buyers with unit demands, private information, and identity‐dependent externalities. We derive the seller's optimal mechanism and characterize its main properties. We show that the probability that a buyer obtains a unit is an increasing function of the externalities he generates and enjoys. Also, the seller's allocation of the units of the good need not be ex post efficient. As an illustration, we apply the model to the problem faced by a developer of a shopping mall who wants to allocate and price its retail space among anchor and non‐anchor stores. We show that a commonly used sequential mechanism is not optimal unless externalities are large enough.     

Price discovery in auction markets: a look inside the black box

Opening mechanisms play a crucial role in information aggregationfollowing the overnight nontrading period. This article examinesthe process of price discovery at the New York Stock Exchangesingle-price opening auction. We develop a theoretical modelto explain the determinants of the opening price and test themodel using order-level data. We show that the presence of designateddealers facilitates price discovery relative to a fully automatedcall auction market. This is consistent with specialists extractinginformation from observing the evolution of the limit orderbook. In addition, the specialist's opening trade reflects noninformationalfactors such as price stabilization requirements.     

Optimal portfolios in commodity futures markets

We develop a general approach to portfolio optimization in futures markets. Following the Heath–Jarrow–Morton (HJM) approach, we model the entire futures price curve at once as a solution of a stochastic partial differential equation. We also develop a general formalism to handle portfolios of futures contracts. In the portfolio optimization problem, the agent invests in futures contracts and a risk-free asset, and her objective is to maximize the utility from final wealth. In order to capture self-consistent futures price dynamics, we study a class of futures price curve models which admit a finite-dimensional realization. More precisely, we establish conditions under which the futures price dynamics can be realized in finite dimensions. Using the finite-dimensional realization, we derive a finite-dimensional form of the portfolio optimization problem and study its solution. We also give an economic interpretation of the coordinate process driving the finite-dimensional realization.     

Optimal product variety in radio markets

A vast theoretical literature explores inefficient market structures in free‐entry equilibria, and previous empirical work demonstrated that excessive entry may obtain in local radio markets. We extend that literature by relaxing the assumption that stations are symmetric, allowing for endogenous horizontal and (unobserved) vertical station differentiation. We find that, in most broadcasting formats, a social planner who takes into account the welfare of market participants eliminates 50%–60% of the observed stations. In 80%–94.9% of markets where high‐quality stations are observed, welfare could be unambiguously improved by converting one such station into low‐quality broadcasting, suggesting local overprovision of quality.     

Optimal consumption policies in illiquid markets

We investigate optimal consumption policies in the liquidity risk model introduced by Pham and Tankov (Math. Finance 18:613–627, 2008). Our main result is to derive smoothness C ¹ results for the value functions of the portfolio/consumption choice problem. As an important consequence, we can prove the existence of the optimal control (portfolio/consumption strategy) which we characterize both in feedback form in terms of the derivatives of the value functions and as the solution of a second-order ODE. Finally, numerical illustrations of the behavior of optimal consumption strategies between two trading dates are given.     

Convergence of trading strategies in continuous double auction markets with boundedly-rational networked traders

This paper considers the convergence of trading strategies among artificial traders connected to one another in a social network and trading in a continuous double auction financial marketplace. Convergence is studied by means of an agent-based simulation model called the Social Network Artificial stoCk marKet model. Six different canonical network topologies (including no-network) are used to represent the possible connections between artificial traders. Traders learn from the trading experiences of their connected neighbours by means of reinforcement learning. The results show that the proportions of traders using particular trading strategies are eventually stable. Which strategies dominate in these stable states depends to some extent on the particular network topology of trader connections and the types of traders.     

Optimal liberalization of financial markets

As financial markets become completely liberalized, countries gain from improved risk sharing, but less wealthy countries can no longer profit from borrowing abroad at the lower rate and reinvesting at home at the higher rate. With decreasing rather than constant returns to capital, the gain from risk sharing is more likely to dominate the loss of the difference between the borrowing rate abroad and the decreasing reinvestment rate at home. Complete liberalization is likely to be optimal for less wealthy countries unless their labor endowment is large, their productivity is large, or holdings by foreigners are small, as in China.     

Call auction algorithm design and market manipulation

It is commonly accepted that closing call auctions provide investors with access to closing prices, reduce volatility and reduce price manipulation. This paper argues that call auction design may influence the achievement of these objectives. The paper focuses on one aspect of call auction design, namely the matching algorithm used to set auction prices. Analysis of two real market cases indicates that different algorithms set different prices. The results also indicate that manipulation has a significant impact on call auction prices, with some algorithm designs more effective than others at reducing the impact of manipulation. Alternate call auction design features, such as volatility extensions, may be necessary to more effectively reduce closing price manipulation.     

Out‐of‐sample stock return predictability in emerging markets

This article builds on the widely debated issue of stock return predictability by applying a broad range of predictor variables and comprehensively considering the in‐sample and out‐of‐sample stock return predictability of ten advanced emerging markets. It compares forecasts from models with a single predictor variable, multiple predictor variables and a combination forecast approach. The results confirm the findings of Welch and Goyal (2008) for US data that only a limited number of individual predictor variables are able to deliver significant out‐of‐sample forecasts. However, a combination forecast approach provides statistically and economically significant out‐of‐sample forecast results.     

Optimal dynamic hedging in incomplete futures markets

This article derives optimal hedging demands for futures contracts from an investor who cannot freely trade his portfolio of primitive assets in the context of either a CARA or a logarithmic utility function. Existing futures contracts are not numerous enough to complete the market. In addition, in the case of CARA, the nonnegativity constraint on wealth is binding, and the optimal hedging demands are not identical to those that would be derived if the constraint were ignored. Fictitiously completing the market, we can characterize the optimal hedging demands for futures contracts. Closed-form solutions exist in the logarithmic case but not in the CARA case, since then a put (insurance) written on his wealth is implicitly bought by the investor. Although solutions are formally similar to those that obtain under complete markets, incompleteness leads in fact to second-best optima.     

Optimal order placement in limit order markets

To execute a trade, participants in electronic equity markets may choose to submit limit orders or market orders across various exchanges where a stock is traded. This decision is influenced by characteristics of the order flows and queue sizes in each limit order book, as well as the structure of transaction fees and rebates across exchanges. We propose a quantitative framework for studying this order placement problem by formulating it as a convex optimization problem. This formulation allows the study of how the optimal order placement decision depends on the interplay between the state of order books, the fee structure, order flow properties and the aversion to execution risk. In the case of a single exchange, we derive an explicit solution for the optimal split between limit and market orders. For the general case of order placement across multiple exchanges, we propose a stochastic algorithm that computes the optimal routing policy and study the sensitivity of the solution to various parameters. Our algorithm does not require an explicit statistical model of order flow but exploits data on recent order fills across exchanges in the numerical implementation of the algorithm to acquire this information through a supervised learning procedure.