Small Extended Formulation for Knapsack Cover Inequalities from Monotone Circuits

Initially developed for the min-knapsack problem, the knapsack cover inequalities are used in the current best relaxations for numerous combinatorial optimization problems of covering type. In spite of their widespread use, these inequalities yield linear programming (LP) relaxations of exponential size, over which it is not known how to optimize exactly in polynomial time. In this paper we address this issue and obtain LP relaxations of quasi-polynomial size that are at least as strong as that given by the knapsack cover inequalities. For the min-knapsack cover problem, our main result can be stated formally as follows: for any $\varepsilon >0$, there is a $(1/\varepsilon)^{O(1)}n^{O(\log n)}$-size LP relaxation with an integrality gap of at most $2+\varepsilon$, where $n$ is the number of items. Prior to this work, there was no known relaxation of subexponential size with a constant upper bound on the integrality gap. Our construction is inspired by a connection between extended formulations and monotone circuit complexity via Karchmer-Wigderson games. In particular, our LP is based on $O(\log^2 n)$-depth monotone circuits with fan-in~$2$ for evaluating weighted threshold functions with $n$ inputs, as constructed by Beimel and Weinreb. We believe that a further understanding of this connection may lead to more positive results complementing the numerous lower bounds recently proved for extended formulations.Comment: 21 page

Economic Shocks and Conflict: The (Absence of?) Evidence from Commodity Price- Working Paper 274

One of the most influential ideas in the study of political instability is that income shocks provoke conflict. “State prize” theories argue that higher revenues increase incentives to capture the state. “Opportunity cost” theories argue that higher prices decrease individual incen-tives to revolt. Both mechanisms are central to leading models of state development and collapse. But are they wellfounded? We examine the effects of exogenous commodity price shocks on conflict and coups, and find little evidence in favor of either theory. Evidence runs especially against the state as prize. We do find weak evidence that the intensity of fighting falls as prices rise—results more consistent with the idea that revenues augment state capacity, not prize-seeking or opportunity cost. Nevertheless, the evidence for any of these income-conflict mecha-nisms is weak at best. We argue that errors and publication bias have likely distorted the theoret-ical and empirical literature on political instability.

Matching and migration: lessons from a resettlement programme in Indonesia

The success of rural relocation and resettlement programmes may be dependent on the transferability of migrants’ skills and experiences to their destinations. New findings from an Indonesian study suggest that relocation programmes should consider providing agricultural extension services to ensure migrants adapt and cope in new environments

Information, Intermediaries, and International Migration

Job seekers face substantial information frictions, especially in international labor markets where intermediaries match prospective migrants with overseas employers. We conducted a randomized trial in Indonesia to explore how information about intermediary quality shapes migration outcomes. Holding access to information about the return to choosing a high-quality intermediary constant, intermediary-specific quality disclosure reduces the migration rate, cutting use of low-quality providers. Workers who do migrate receive better pre-departure preparation and have improved experiences abroad, despite no change in occupation or destination. These results are not driven by changes in beliefs about average provider quality or the return to migration. Nor does selection explain improved outcomes for those who migrate with quality disclosure. Together, our findings are consistent with an increase in the option value of search: with better ability to differentiate offer quality, workers search longer, select higher-quality intermediaries, and ultimately have better migration experiences

Social Protection in Indonesia:Past Experiences and Lessons for the Future.

Prior to the Asian financial crisis, social protection in Indonesia was largely based on informal arrangements. When the country sank into a deep social and economic crisis in 1998, the government had no alternative but to create new, more formal social safety nets explicitly aimed at helping the chronic poor and vulnerable non-poor cope with the impact of the crisis. A comprehensive set of safety net programs covered food security, employment creation, education, health, and community empowerment. Several years after the crisis as the economy slowly recovered and welfare stabilized around pre-crisis levels, the government redesigned several of these programs while discontinuing others. Throughout this latter, post-crisis period, the government also implemented a range of new social protection programs, including several conditional and unconditional cash transfer programs, to replace highly regressive fuel subsidies. Recently, the government has formed a National Team for the Acceleration of Poverty Reduction (TNP2K) with the mandate to reduce poverty incidence to 8% by 2014. This essay analyses Indonesia‟s experience with social protection during and after the crisis, drawing key lessons for the future of social protection policy in Indonesia

It's All in the Timing:Household Expenditure and Labor Supply Responses to Unconditional Cash Transfers.

Targeted cash transfer programs have been an important policy tool in developing countries. This paper considers (i) how the timing of transfers affects household expenditure and labor supply responses, and (ii) how household expectations shape our interpretation of those responses. We study these issues in the context of a short-term program that provided quarterly unconditional transfers of US$30 to over 19 million households in Indonesia. Our empirical strategy relies on nationally representative panel data, difference-in-difference re-weighting estimators, and the staggered rollout of the second quarterly transfer. On average, beneficiary households that received the two full transfers by early 2006 did not differ from comparable nonbeneficiaries in terms of per capita expenditure growth and changes in labor supply per adult. However, beneficiaries still awaiting their second transfer reported a 7 percentage point lower expenditure growth and a reduction in labor supply by an additional 1.5 hours per adult per week. The expenditure differences dissipated by early 2007, several months after the final transfer were received by all beneficiaries. We also exploit variation in transfers per capita to identify a small marginal propensity to consume out of transfer income (around 0.10). We reconcile the empirical results with the predictions of a simple permanent income model, consider rival (missing) data-driven explanations, and document similar household responses to other transitory changes in income

It's All in the Timing:Household Expenditure and Labor Supply Responses to Unconditional Cash Transfers.

Targeted cash transfer programs have been an important policy tool in developing countries. This paper considers (i) how the timing of transfers affects household expenditure and labor supply responses, and (ii) how household expectations shape our interpretation of those responses. We study these issues in the context of a short-term program that provided quarterly unconditional transfers of US$30 to over 19 million households in Indonesia. Our empirical strategy relies on nationally representative panel data, difference-in-difference re-weighting estimators, and the staggered rollout of the second quarterly transfer. On average, beneficiary households that received the two full transfers by early 2006 did not differ from comparable nonbeneficiaries in terms of per capita expenditure growth and changes in labor supply per adult. However, beneficiaries still awaiting their second transfer reported a 7 percentage point lower expenditure growth and a reduction in labor supply by an additional 1.5 hours per adult per week. The expenditure differences dissipated by early 2007, several months after the final transfer were received by all beneficiaries. We also exploit variation in transfers per capita to identify a small marginal propensity to consume out of transfer income (around 0.10). We reconcile the empirical results with the predictions of a simple permanent income model, consider rival (missing) data-driven explanations, and document similar household responses to other transitory changes in income

Finding the Poor vs. Measuring Their Poverty: Exploring the Drivers of Targeting Effectiveness in Indonesia.

Centralised targeting registries are increasingly used to allocate social assistance benefits in developing countries. This paper provides the first attempt to identify the relative importance of two key design issues for targeting accuracy: (1) which households to survey for inclusion in the targeting registry and (2) how to rank surveyed households. We evaluate the performance of Indonesia’s Unified Database for Social Protection Programmes (UDB), the largest targeting registry in the world, which is used to provide social assistance to more than 25 million households. Linking administrative data with an independent household survey, we find that the UDB system is more progressive than previous targeting approaches used in Indonesia, leading to a decrease in benefit leakage to non-poor households. However, if poor households are not surveyed in the first place, even a perfect ranking method cannot prevent their exclusion. Under a simulation that considers enumerating and estimating proxy-means testing (PMT) scores for all households (as in a census), we estimate a one-third decrease in undercoverage compared to focusing on households that have been registered in the UDB. Investigating household- and community-level correlates of misenumeration and misclassification, we find evidence that local communities use different definitions of poverty and have better information on the welfare status of their members

Deterring illegal entry: migrant sanctions and recidivism in border apprehensions

During the 2008 to 2012 period, the US Border Patrol enacted new sanctions on migrants apprehended while attempting to enter the United States illegally. Using administrative records on apprehensions of Mexican nationals that include fingerprint-based IDs and other details, we detect if an apprehended migrant is subject to penalties and if he is later reapprehended. Exploiting plausibly random variation in the rollout of sanctions, we estimate econometrically that exposure to penalties reduced the 18-month reapprehension rate for males by 4.6 to 6.1 percentage points off of a baseline rate of 24.2 percent. These magnitudes imply that sanctions can account for 28 to 44 percent of the observed decline in recidivism in apprehensions. Further results suggest that the drop in recidivism was associated with a reduction in attempted illegal entry.https://sites.google.com/site/samuelbazzi/research/BBHRW_Manuscript.pdf?attredirects=0Published versio