Low-Cost Learning via Active Data Procurement

We design mechanisms for online procurement of data held by strategic agents for machine learning tasks. The challenge is to use past data to actively price future data and give learning guarantees even when an agent's cost for revealing her data may depend arbitrarily on the data itself. We achieve this goal by showing how to convert a large class of no-regret algorithms into online posted-price and learning mechanisms. Our results in a sense parallel classic sample complexity guarantees, but with the key resource being money rather than quantity of data: With a budget constraint $B$, we give robust risk (predictive error) bounds on the order of $1/\sqrt{B}$. Because we use an active approach, we can often guarantee to do significantly better by leveraging correlations between costs and data. Our algorithms and analysis go through a model of no-regret learning with $T$ arriving pairs (cost, data) and a budget constraint of $B$. Our regret bounds for this model are on the order of $T/\sqrt{B}$ and we give lower bounds on the same order.Comment: Full version of EC 2015 paper. Color recommended for figures but nonessential. 36 pages, of which 12 appendi

CEO equity incentive, board gender diversity, and share repurchases

This study investigates the effect of CEO equity incentive on share repurchase. We further consider the influence of board gender diversity on the relation between CEO equity incentives and share repurchase. Using a sample of the Taiwan Stock Exchange and Taipei Exchange listed companies from 2002 to 2016, we document that, relative to lower equity incentive, CEOs with higher equity incentive are more likely to buy back shares, in particular when their stock prices are perceived as undervalued. Furthermore, we also find that board gender diversity mitigates the relation between CEO equity incentive and share buyback

L'acquisition de la liaison dans les groupes nominaux et les groupes verbaux

The liaison, as a special sandhi phenomenon in French, has been a popular subject of debate in linguistics. The usage-based theory proposed that the liaison is a construction larger than just one word, and the noun and verb phrases are two sub-constructions. Chevrot et al. (2009) proposed that children, at the first stage of acquisition, construct a schema with a word1 and several exemplars of word2. At the second stage, children construct a schema in which the consonant of liaison is determined by the word1. However, while the acquisition of liaisons in noun phrases, i. e. determinant-noun, has been largely discussed, the researches on the acquisition of liaisons in verb phrases remain limited. In this article, a comparison was drawn between the development of liaisons in both noun and verb phrases. The children were tested with a nomination test, which included 18 noun phrases and 30 verb phrases. The results revealed that the children learned the liaisons in verb phrases faster than in noun phrases. The schema of second acquisition stage appeared at around the age of 5 in the noun phrases while it is already developed at 3;1 – 3;11 (our youngest age group) in the verb phrases. The errors of replacement confirmed that children had several exemplars of word2 with different initial consonants, and as the occurrence of these errors slowed, the children moved from the first stage to the second stage of acquisition. It was also noted that the acquisition of liaisons in these two grammatical phrases is correlated, implying that they belong to the same construction. Finally, the role of frequency in development was examined. The results showed that a high frequency of word1-word2 sequences facilitate the development of acquisitions of liaisons. A qualitative analysis of nine children younger than 37 months is provided at the end. It was noted that children at an early age, children already showed a better performance in verb phrases than in noun phrases.La liaison, comme un phénomène de sandhi spécial en français, est un sujet populaire de débat en linguistique. Les théories basées sur l'usage proposent que la liaison est une construction au-dessus d'un seul mot et que les groupes nominaux et les groupes verbaux sont deux sous-constructions de la liaison. Chevrot et al. (2009) proposent que dans le premier stade, les enfants construisent un schéma formé d'un mot 1 et plusieurs variantes du mot 2, puis au deuxième stade, les enfants construisent un schéma que la consonne de liaison est déterminée par le mot 1. Cependant, quand l'acquisition dans les groupes nominaux est largement discutée, les recherches sur l'acquisition de liaison dans les groupes verbaux le sont beaucoup moins. Dans cet article, nous avons comparé le développement de l'acquisition de liaison dans les deux groupes. Nous avons testé les enfants avec deux tâches de dénomination, incluant 18 groupes nominaux et 30 groupes verbaux. Nos résultats ont montré que les enfants apprennent la liaison plus vite dans les groupes verbaux que dans les groupes nominaux. Les erreurs par remplacement confirment que les enfants ont plusieurs variantes du mot2 avec différentes consonnes initiales et comme la production d'erreur par remplacement a diminuée, les enfants ont changé du schéma de stade 1 à ce de stade 2. Nous avons également noté que les acquisitions dans les deux groupes sont corrélées, montrant qu'ils sont dans la même construction. Finalement, nous avons examiné le rôle de fréquence dans l'acquisition. Nous avons montré que la fréquence haute des séquences mot1-mot2 favorise le développement de l'acquisition de liaison puis nous avons effectué une analyse qualitative de neuf enfants de moins de 37 mois. Nous avons noté que les enfants à l'âge précoce montrent de meilleure performance dans les groupes verbaux et dans les groupes nominaux

Bank Loan Covenants and Accrual Quality

We examine whether financial covenants in loan contracts motivate banks to monitor borrowers’ financial reporting practices and result in a higher quality of reported accruals. We document that, relative to loans without financial covenants, loans with financial covenants lead to a significant improvement in accrual quality measured by the extent to which accruals can be mapped into cash flows. The effect of loan covenants on accrual quality is stronger when external monitoring by non-bank stakeholders (i.e., institutional investors and financial analysts) is weaker. Furthermore, initiations of bank loans with financial covenants are related to subsequent improvements in analysts’ information environment. The evidence supports the view that bank monitoring improves accounting quality

Extracellular RNA in a single droplet of human serum reflects physiologic and disease states.

Extracellular RNAs (exRNAs) are present in human serum. It remains unclear to what extent these circulating exRNAs may reflect human physiologic and disease states. Here, we developed SILVER-seq (Small Input Liquid Volume Extracellular RNA Sequencing) to efficiently sequence both integral and fragmented exRNAs from a small droplet (5 μL to 7 μL) of liquid biopsy. We calibrated SILVER-seq in reference to other RNA sequencing methods based on milliliters of input serum and quantified droplet-to-droplet and donor-to-donor variations. We carried out SILVER-seq on more than 150 serum droplets from male and female donors ranging from 18 y to 48 y of age. SILVER-seq detected exRNAs from more than a quarter of the human genes, including small RNAs and fragments of mRNAs and long noncoding RNAs (lncRNAs). The detected exRNAs included those derived from genes with tissue (e.g., brain)-specific expression. The exRNA expression levels separated the male and female samples and were correlated with chronological age. Noncancer and breast cancer donors exhibited pronounced differences, whereas donors with or without cancer recurrence exhibited moderate differences in exRNA expression patterns. Even without using differentially expressed exRNAs as features, nearly all cancer and noncancer samples and a large portion of the recurrence and nonrecurrence samples could be correctly classified by exRNA expression values. These data suggest the potential of using exRNAs in a single droplet of serum for liquid biopsy-based diagnostics

IMMEDIATE EFFECTS OF WARM UP BY OVERWEIGHED BAT IMPLEMENT ON BAT SWING VELOCITY

The purpose of this study was to investigate the immediate effects of warming up by overweighed bat implement on bat swing velocity. Five softball players worked in this experiment and processed the following steps: swing official bat with and without overweight warm-ups (5 and 10 times). The maximal velocity of official bat swing was recorded by a 3-D cinematograph. By one-way ANOVA, the results were described as follows: the maximal velocity of official bat swing after 5-swingings of the overweight bat was greater than that without warm up (F=9.28,

Performative Prediction with Bandit Feedback: Learning through Reparameterization

Performative prediction, as introduced by Perdomo et al. (2020), is a framework for studying social prediction in which the data distribution itself changes in response to the deployment of a model. Existing work on optimizing accuracy in this setting hinges on two assumptions that are easily violated in practice: that the performative risk is convex over the deployed model, and that the mapping from the model to the data distribution is known to the model designer in advance. In this paper, we initiate the study of tractable performative prediction problems that do not require these assumptions. To tackle this more challenging setting, we develop a two-level zeroth-order optimization algorithm, where one level aims to compute the distribution map, and the other level reparameterizes the performative prediction objective as a function of the induced data distribution. Under mild conditions, this reparameterization allows us to transform the non-convex objective into a convex one and achieve provable regret guarantees. In particular, we provide a regret bound that is sublinear in the total number of performative samples taken and only polynomial in the dimension of the model parameter

When Social Influence Meets Item Inference

Research issues and data mining techniques for product recommendation and viral marketing have been widely studied. Existing works on seed selection in social networks do not take into account the effect of product recommendations in e-commerce stores. In this paper, we investigate the seed selection problem for viral marketing that considers both effects of social influence and item inference (for product recommendation). We develop a new model, Social Item Graph (SIG), that captures both effects in form of hyperedges. Accordingly, we formulate a seed selection problem, called Social Item Maximization Problem (SIMP), and prove the hardness of SIMP. We design an efficient algorithm with performance guarantee, called Hyperedge-Aware Greedy (HAG), for SIMP and develop a new index structure, called SIG-index, to accelerate the computation of diffusion process in HAG. Moreover, to construct realistic SIG models for SIMP, we develop a statistical inference based framework to learn the weights of hyperedges from data. Finally, we perform a comprehensive evaluation on our proposals with various baselines. Experimental result validates our ideas and demonstrates the effectiveness and efficiency of the proposed model and algorithms over baselines.Comment: 12 page