I am currently a fifth year Ph.D student in the Department of Economics at Southern Methodist University. My research interests include matching theory, market design, game theory and applied microeconomic theory. I will join the School of Economics at Shanghai University of Finance and Economics (SUFE). Email: xiangh@smu.edu Phone: +1 (469) 559-8249 CV (pdf) |

**Research**

Ex-ante fair random allocation

**Job market paper****Abstract**When allocating indivisible objects, agents might have equal priority rights for some objects. A common practice is to break the ties using a lottery and randomize over deterministic allocation mechanisms. Such randomizations usually lead to unfairness and inefficiency ex-ante. We propose a concept of ex-ante fairness and show the existence of an agent-optimal ex-ante fair solution. Ex- ante fair random allocations are generated using "allocation by division", a new method of generating random allocations from deterministic allocation mechanisms. Insights from the two-sided matching theory and the recent random assignment literature are unified and extended. The set of ex-ante fair random allocations forms a complete lattice under first-order stochastic dominance relations. The agent-optimal ex-ante fair mechanism includes both the deferred acceptance algorithm and the probabilistic serial mechanism as special cases.

Stable and efficient resource allocation under weak priorities

*R&R Games and Economic Behavior*

**Abstract**We study the indivisible object allocation problem without monetary transfer, in which each object is endowed with a weak priority ordering over agents. It is well known that stability is generally not compatible with efficiency in this problem. We characterize the priority structures for which a stable and efficient assignment always exists, as well as the priority structures that admit a stable, efficient and (group) strategy-proof rule. While house allocation problems and housing markets are two classic families of allocation problems that admit a stable, efficient and group strategy-proof rule, any priority-augmented allocation problem with more than three objects admits such a rule if and only if it is decomposable into a sequence of subproblems, each of which has the structure of a house allocation problem or a housing market. One corollary of this result is that there exists a stable hierarchical exchange rule (Pápai, 2000) if and only if there exists a stable, efficient and group strategy-proof rule.

On the consistency of random serial dictatorship,

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**Economics Letters***Volume 145, 168-171, 2016*

**Abstract**The random serial dictatorship (RSD) can be generalized to indivisible object allocation problems allowing fractional endowments such that symmetry, ex-post efficiency and strategy-proofness are preserved. However, there exists a consistent extension of RSD if and only if the population is less than four. The inconsistency of the generalized RSD is a common feature of strategy-proof rules that satisfy minimal fairness and efficiency properties: symmetry, ex-post efficiency, consistency and strategy-proofness are not compatible.

Random assignment respecting group priorities

**Abstract**When allocating indivisible objects, agents may be partitioned into several groups and different groups are granted different priority rights. Group-wise random serial dictatorship (GRSD) and group-wise probabilistic serial mechanism (GPS) can be applied to such problems to restore fairness within and across groups. GPS outperforms GRSD not only in efficiency but also in stability ex-ante. The family of group-wise eating mechanisms characterizes the set of sd-efficient and ex-ante stable assignments, while the family of asymmetric GRSDs characterizes the set of ex-post stable and efficient assignments. However, GRSD satisfies a mild consistency concept based on Bayesian update while GPS does not, and consequently the advantages of GPS may disappear in cases of non-simultaneous assignment. We finish by characterizing GPS and considering comparative statics results as the group structure becomes more dense.