Distortion control for delay-sensitive sources

We investigate the problem of finding minimum-distortion policies for streaming delay-sensitive but distortion-tolerant data. We consider cross-layer approaches which exploit the coupling between presentation and transport layers. We make the natural assumption that the distortion function is convex and decreasing. We focus on a single source-destination pair and analytically find the optimum transmission policy when the transmission is done over an error-free channel. This optimum policy turns out to be independent of the exact form of the convex and decreasing distortion function. Then, for a packet-erasure channel, we analytically find the optimum open-loop transmission policy, which is also independent of the form of the convex distortion function. We then find computationally efficient closed-loop heuristic policies and show, through numerical evaluation, that they outperform the open-loop policy and have near optimal performance.

The short arm of the law: judicial institutions and local governance in Brazil

This paper estimates the effect of judicial institutions on governance at the local level in Brazil. Our estimation strategy exploits a unique institutional feature of state judiciary branches which assigns prosecutors and judges to the most populous among contiguous counties forming a judiciary district. As a result of this assignment mechanism there are counties with nearly identical populations, some with and some without local judicial presence, which we exploit to impute counterfactual outcomes. Conditional on observable county characteristics, offenses per civil servant are about 35% lower in counties that have a local seat of the state judiciary. The lower incidence of infractions stems mostly from fewer violations of financial management regulations by local administrators, fewer instances of problems in project execution and project managment, fewer cases of non-existent or ineffective civil society oversight and fewer cases of improper handling of remittances to local residents.

Civil conflict and human capital accumulation: The long-term effects of political violence in Perú

This paper provides empirical evidence of the persistent effect of exposure to political violence on humancapital accumulation. I exploit the variation in conflict location and birth cohorts to identify the longandshort-term effects of the civil war on educational attainment. Conditional on being exposed toviolence, the average person accumulates 0.31 less years of education as an adult. In the short-term,the effects are stronger than in the long-run; these results hold when comparing children within thesame household. Further, exposure to violence during early childhood leads to permanent losses. I alsoexplore the potential causal mechanisms.

Banks and development: Jewish communities in the Italian Renaissance and current economic performance

Are differences in local banking development long-lasting? Do they affect long-term economic performance?I answer these questions by relying on an historical development that occurred in Italian cities during the 15thcentury. A sudden change in the Catholic doctrine had driven the Jews toward money lending. Cities thatwere hosting Jewish communities developed complex banking institutions for two reasons: first, the Jews werethe only people in Italy who were allowed to lend for a profit and, second, the Franciscan reaction to Jewishusury led to the creation of charity lending institutions, the Monti di Pietà, that have survived until today andhave become the basis of the Italian banking system. Using Jewish demography in 1500 as an instrument, Iprovide evidence of (1) an extraordinary persistence in the level of banking development across Italian cities (2)large effects of current local banking development on per-capita income. Additional firm-level analyses suggestthat well-functioning local banks exert large effects on aggregate productivity by reallocating resources towardmore efficient firms. I exploit the expulsion of the Jews from the Spanish territories in Italy in 1541 to arguethat my results are not driven by omitted institutional, cultural and geographical characteristics. In particular,I show that, in Central Italy, the difference in current income between cities that hosted Jewish communitiesand cities that did not exists only in those regions that were not Spanish territories in the 16th century.

Asymptotic robust inferences in the analysis of mean and covariance structures

Structural equation models are widely used in economic, socialand behavioral studies to analyze linear interrelationships amongvariables, some of which may be unobservable or subject to measurementerror. Alternative estimation methods that exploit different distributionalassumptions are now available. The present paper deals with issues ofasymptotic statistical inferences, such as the evaluation of standarderrors of estimates and chi--square goodness--of--fit statistics,in the general context of mean and covariance structures. The emphasisis on drawing correct statistical inferences regardless of thedistribution of the data and the method of estimation employed. A(distribution--free) consistent estimate of $\Gamma$, the matrix ofasymptotic variances of the vector of sample second--order moments,will be used to compute robust standard errors and a robust chi--squaregoodness--of--fit squares. Simple modifications of the usual estimateof $\Gamma$ will also permit correct inferences in the case of multi--stage complex samples. We will also discuss the conditions under which,regardless of the distribution of the data, one can rely on the usual(non--robust) inferential statistics. Finally, a multivariate regressionmodel with errors--in--variables will be used to illustrate, by meansof simulated data, various theoretical aspects of the paper.

Immigration and housing booms: Evidence from Spain

We estimate empirically the effect of immigration on house prices and residentialconstruction activity in Spain over the period 1998-2008. This decade is characterized by both aspectacular housing market boom and a stunning immigration wave. We exploit the variation inimmigration across Spanish provinces and construct an instrument based on the historicallocation patterns of immigrants by country of origin. The evidence points to a sizeable causaleffect of immigration on both prices and quantities in the housing market. Between 1998 and2008, the average Spanish province received an immigrant inflow equal to 17% of the initialworking-age population. We estimate that this inflow increased house prices by about 52% andis responsible for 37% of the total construction of new housing units during the period. Thesefigures imply that immigration can account for roughly one third of the housing boom, both interms of prices and new construction.

Parallel scheduling of multiclass M/M/m queues: Approximate and heavy-traffic optimization of achievable performance

We address the problem of scheduling a multiclass $M/M/m$ queue with Bernoulli feedback on $m$ parallel servers to minimize time-average linear holding costs. We analyze the performance of a heuristic priority-index rule, which extends Klimov's optimal solution to the single-server case: servers select preemptively customers with larger Klimov indices. We present closed-form suboptimality bounds (approximate optimality) for Klimov's rule, which imply that its suboptimality gap is uniformly bounded above with respect to (i) external arrival rates, as long as they stay within system capacity;and (ii) the number of servers. It follows that its relativesuboptimality gap vanishes in a heavy-traffic limit, as external arrival rates approach system capacity (heavy-traffic optimality). We obtain simpler expressions for the special no-feedback case, where the heuristic reduces to the classical $c \mu$ rule. Our analysis is based on comparing the expected cost of Klimov's ruleto the value of a strong linear programming (LP) relaxation of the system's region of achievable performance of mean queue lengths. In order to obtain this relaxation, we derive and exploit a new set ofwork decomposition laws for the parallel-server system. We further report on the results of a computational study on the quality of the $c \mu$ rule for parallel scheduling.

Voting after the bombing: Can terrorist attacks change the outcome of democratic elections?

Economists have recently turned their attention to the effects of terrorism. One much debated effect of terrorist attacks is its impact on the results of democratic elections. We use the electoral consequences of the terrorist attacks of the 11-M in Madrid to analyze this issue. We consider this particular experiment since the attack took place only three days before the 2004 Congressional Election, which allows the use of credible identification criteria. In particular, we use the advance voting by Spanish residents abroad, who cast their vote before the terrorist attack, to identify the effect of the bombing. We exploit this macabre natural experiment to run a difference-in-differences estimation using data on three consecutive Congressional elections. Our empirical results indicate that a terrorist attack can have a large impact on the outcome of democratic elections.

The importance of relative performance feedback information: Evidence from a natural experiment using high school students

We study the effect of providing relative performance feedback information onperformance, when individuals are rewarded according to their absolute performance. Anatural experiment that took place in a high school offers an unusual opportunity to testthis effect in a real-effort setting. For one year only, students received information thatallowed them to know whether they were performing above (below) the class average aswell as the distance from this average. We exploit a rich panel data set and find that theprovision of this information led to an increase of 5% in students grades. Moreover, theeffect was significant for the whole distribution. However, once the information wasremoved, the effect disappeared. To rule out the concern that the effect may beartificially driven by teachers within the school, we verify our results using nationallevel exams (externally graded) for the same students, and the effect remains.

A comparison of stock market mechanisms

This paper studies the relationship between the amount of publicinformation that stock market prices incorporate and the equilibriumbehavior of market participants. The analysis is framed in a static, NREEsetup where traders exchange vectors of assets accessing multidimensionalinformation under two alternative market structures. In the first(the unrestricted system), both informed and uninformed speculators cancondition their demands for each traded asset on all equilibrium prices;in the second (the restricted system), they are restricted to conditiontheir demand on the price of the asset they want to trade. I show thatinformed traders incentives to exploit multidimensional privateinformation depend on the number of prices they can condition upon whensubmitting their demand schedules, and on the specific price formationprocess one considers. Building on this insight, I then give conditionsunder which the restricted system is more efficient than the unrestrictedsystem.

The optimal length of contracts with application to outsourcing

This paper resolves three empirical puzzles in outsourcing by formalizing the adaptationcost of long-term performance contracts. Side-trading with a new partner alongside a long-term contract (to exploit an adaptation-requiring investment) is usually less effective than switching to the new partner when the contract expires. So long-term contracts that prevent holdup of specific investments may induce holdup of adaptation investments. Contract length therefore trades of specific and adaptation investments. Length should increase with the importance and specificity of self-investments, and decrease with the importance of adaptation investments for which side-trading is ineffective. My general model also shows how optimal length falls with cross-investments and wasteful investments.

Experiencing simulated outcomes

Whereas much literature has documented difficulties in making probabilistic inferences, it hasalso emphasized the importance of task characteristics in determining judgmental accuracy.Noting that people exhibit remarkable efficiency in encoding frequency information sequentially,we construct tasks that exploit this ability by requiring people to experience the outcomes ofsequentially simulated data. We report two experiments. The first involved seven well-knownprobabilistic inference tasks. Participants differed in statistical sophistication and answered withand without experience obtained through sequentially simulated outcomes in a design thatpermitted both between- and within-subject analyses. The second experiment involvedinterpreting the outcomes of a regression analysis when making inferences for investmentdecisions. In both experiments, even the statistically naïve make accurate probabilistic inferencesafter experiencing sequentially simulated outcomes and many prefer this presentation format. Weconclude by discussing theoretical and practical implications.

Revenue management under general discrete choice model of consumer behavior

Customer choice behavior, such as 'buy-up' and 'buy-down', is an importantphe-nomenon in a wide range of industries. Yet there are few models ormethodologies available to exploit this phenomenon within yield managementsystems. We make some progress on filling this void. Specifically, wedevelop a model of yield management in which the buyers' behavior ismodeled explicitly using a multi-nomial logit model of demand. Thecontrol problem is to decide which subset of fare classes to offer ateach point in time. The set of open fare classes then affects the purchaseprobabilities for each class. We formulate a dynamic program todetermine the optimal control policy and show that it reduces to a dynamicnested allocation policy. Thus, the optimal choice-based policy caneasily be implemented in reservation systems that use nested allocationcontrols. We also develop an estimation procedure for our model based onthe expectation-maximization (EM) method that jointly estimates arrivalrates and choice model parameters when no-purchase outcomes areunobservable. Numerical results show that this combined optimization-estimation approach may significantly improve revenue performancerelative to traditional leg-based models that do not account for choicebehavior.

The effect of divorce laws on divorce rates in Europe

This paper analyzes a panel of 18 European countries spanning from 1950 to 2003 toexamine the extent to which the legal reforms leading to easier divorce that took placeduring the second half of the 20th century have contributed to the increase in divorce rates across Europe. We use a quasi-experimental set-up and exploit the different timing of the reforms in divorce laws across countries. We account for unobserved country-specificfactors by introducing country fixed effects, and we include country-specific trends tocontrol for time-varying factors at the country level that may be correlated with divorcerates and divorce laws, such as changing social norms or slow moving demographictrends. We find that the reforms were followed by significant increases in divorce rates.Overall, we estimate that the introduction of no-fault, unilateral divorce increased thedivorce rate by about 1, a sizeable effect given the average rate of 4.2 divorces per 1,000married people in 2002.

The informational value of incumbency

This paper proposes an argument that explains incumbency advantage without recurring to the collective irresponsibility of legislatures. For that purpose, we exploit the informational value of incumbency: incumbency confers voters information about governing politicians not available from challengers. Because there are many reasons for high reelection rates different from incumbency status, we propose a measure of incumbency advantage that improves the use of pure reelection success. We also study the relationship between incumbency advantage and ideological and selection biases. An important implication of our analysis is that the literature linking incumbency and legislature irresponsibility most likely provides an overestimation of the latter.