Multi-outcome and Multidimensional Market Scoring Rules

Hanson's market scoring rules allow us to design a prediction market that still gives useful information even if we have an illiquid market with a limited number of budget-constrained agents. Each agent can "move" the current price of a market towards their prediction. While this movement still occurs in multi-outcome or multidimensional markets we show that no market-scoring rule, under reasonable conditions, always moves the price directly towards beliefs of the agents. We present a modified version of a market scoring rule for budget-limited traders, and show that it does have the property that, from any starting position, optimal trade by a budget-limited trader will result in the market being moved towards the trader's true belief. This mechanism also retains several attractive strategic properties of the market scoring rule

Learning Political Science with Prediction Markets: An Experimental Study

Prediction markets are designed to aggregate the information of many individuals to forecast future events. These markets provide participants with an incentive to seek information and a forum for interaction, making markets a promising tool to motivate student learning. We carried out a quasi-experiment in an introductory political science class to study the effect of prediction markets on student engagement with the course topics. Although we found no significant improvement in students' enthusiasm or extent of topical reading, we did find that those students who were already reading broadly at the course start were more likely to trade actively in the markets. These findings indicate that prediction markets may be most successful as an education tool in settings, like graduate education, where individuals are already knowledgeable about the topics of the market, instead of an introductory learning context.National Science Foundation grant CCF-0728768.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111010/1/S1049096511002113a.pdf111Description of S1049096511002113a.pdf : Main Articl

SI 583 - Recommender Systems, Winter 2009

Recommender systems guide people to interesting materials based on information from other people. A large design space of alternative ways to organize such systems exists. The information that other people provide may come from explicit ratings, tags, or reviews, or implicitly from how they spend their time or money. The information can be aggregated and used to select, filter, or sort items. The recommendations may be personalized to the preferences of different users.http://deepblue.lib.umich.edu/bitstream/2027.42/78193/5/Sami-SI583-W09-Lectures-Class3.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/6/Sami-SI583-W09-Lectures-Class1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/7/Sami-SI583-W09-Lectures-Class6.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/8/Sami-Resnick-SI583-W09-Lectures-Class8.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/9/Sami-Resnick-SI583-W09-Lectures-Class8.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/10/Sami-SI583-W09-Lectures-Class9.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/11/Sami-SI583-W09-Lectures-Class1.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/12/Sami-Resnick-SI583-W09-Lectures-Class2.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/13/Sami-SI583-W09-Lectures-Class5.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/14/Sami-SI583-W09-Lectures-Class13.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/15/Sami-Resnick-SI583-W09-Lectures-Class2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/16/Sami-SI583-W09-Lectures-Class11.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/17/Sami-Resnick-SI583-W09-Lectures-Class7.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/18/Sami-SI583-W09-Lectures-Class13.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/19/Sami-SI583-W09-Lectures-Class1.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/20/Sami-SI583-W09-Lectures-Class5.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/21/Sami-Resnick-SI583-W09-Lectures-Class7.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/22/Sami-SI583-W09-Lectures-Class3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/23/Sami-SI583-W09-Lectures-Class12.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/24/Sami-SI583-W09-Lectures-Class11.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/25/Sami-SI583-W09-ReadingList.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/26/Sami-SI583-W09-Lectures-Class10.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/27/Sami-SI583-W09-Lectures-Class9.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/28/Sami-Resnick-SI583-W09-Lectures-Class7.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/29/Sami-SI583-W09-Lectures-Class3.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/30/Sami-SI583-W09-Lectures-Class5.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/31/Sami-SI583-W09-Lectures-Class6.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/32/Sami-SI583-W09-Lectures-Class10.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/33/Sami-SI583-W09-ReadingList.dochttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/34/Sami-SI583-W09-Lectures-Class13.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/35/Sami-SI583-W09-Lectures-Class6.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/36/Sami-SI583-W09-Lectures-Class10.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/37/Sami-SI583-W09-Lectures-Class9.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/38/Sami-SI583-W09-Lectures-Class11.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/39/Sami-Resnick-SI583-W09-Lectures-Class2.odphttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/40/Sami-Resnick-SI583-W09-Lectures-Class8.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/41/Sami-SI583-W09-ReadingList.odthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/42/Sami-SI583-W09-Lectures-Class12.ppthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/43/Sami-SI583-W09-Lectures-Class12.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/44/Sami-SI583-W09-Syllabus.odthttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/45/Sami-SI583-W09-Syllabus.dochttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/46/Sami-SI583-W09-Syllabus.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78193/47/si583-winter2009.zi

The Influence Limiter: Provably Manipulation-Resistant Recommender Systems (Appendix)

Appendix containing proofs omitted from Resnick and Sami,"The Influence Limiter: Provably Manipulation-Resistant Recommender Systems", ACM Recommender Systems Conference 2007.http://deepblue.lib.umich.edu/bitstream/2027.42/55415/1/recsys-appendix.pd

Acute ischemic stroke in a university hospital intensive care unit : 1-year costs and outcome

Background and purpose Little is currently known about the cost-effectiveness of intensive care of acute ischemic stroke (AIS). We evaluated 1-year costs and outcome for patients with AIS treated in the intensive care unit (ICU). Materials and methods A single-center retrospective study of patients admitted to an academic ICU with AIS between 2003 and 2013. True healthcare expenditure was obtained up to 1 year after admission and adjusted to consumer price index of 2019. Patient outcome was 12-month functional outcome and mortality. We used multivariate logistic regression analysis to identify independent predictors of favorable outcomes and linear regression analysis to assess factors associated with costs. We calculated the effective cost per survivor (ECPS) and effective cost per favorable outcome (ECPFO). Results The study population comprised 154 patients. Reasons for ICU admission were: decreased consciousness level (47%) and need for respiratory support (40%). There were 68 (44%) 1 year survivors, of which 27 (18%) had a favorable outcome. High age (odds ratio [OR] 0.95, 95% confidence interval [CI] 0.91-0.98) and high hospital admission National Institutes of Health Stroke Scale score (OR 0.92, 95% CI 0.87-0.97) were independent predictors of poor outcomes. Increased age had a cost ratio of 0.98 (95% CI 0.97-0.99) per added year. The ECPS and ECPFO were 115,628euro and 291,210euro, respectively. Conclusions Treatment of AIS in the ICU is resource-intense, and in an era predating mechanical thrombectomy the outcome is often poor, suggesting a need for further research into cost-efficacy of ICU care for AIS patients.Peer reviewe

High Accuracy Decoding of Movement Target Direction in Non-Human Primates Based on Common Spatial Patterns of Local Field Potentials

BACKGROUND: The current development of brain-machine interface technology is limited, among other factors, by concerns about the long-term stability of single- and multi-unit neural signals. In addition, the understanding of the relation between potentially more stable neural signals, such as local field potentials, and motor behavior is still in its early stages. METHODOLOGY/PRINCIPAL FINDINGS: We tested the hypothesis that spatial correlation patterns of neural data can be used to decode movement target direction. In particular, we examined local field potentials (LFP), which are thought to be more stable over time than single unit activity (SUA). Using LFP recordings from chronically implanted electrodes in the dorsal premotor and primary motor cortex of non-human primates trained to make arm movements in different directions, we made the following observations: (i) it is possible to decode movement target direction with high fidelity from the spatial correlation patterns of neural activity in both primary motor (M1) and dorsal premotor cortex (PMd); (ii) the decoding accuracy of LFP was similar to the decoding accuracy obtained with the set of SUA recorded simultaneously; (iii) directional information varied with the LFP frequency sub-band, being greater in low (0.3-4 Hz) and high (48-200 Hz) frequency bands than in intermediate bands; (iv) the amount of directional information was similar in M1 and PMd; (v) reliable decoding was achieved well in advance of movement onset; and (vi) LFP were relatively stable over a period of one week. CONCLUSIONS/SIGNIFICANCE: The results demonstrate that the spatial correlation patterns of LFP signals can be used to decode movement target direction. This finding suggests that parameters of movement, such as target direction, have a stable spatial distribution within primary motor and dorsal premotor cortex, which may be used for brain-machine interfaces

Gaming Prediction Markets: Equilibrium Strategies with a Market Maker

We study the equilibrium behavior of informed traders interacting with market scoring rule (MSR) market makers. One attractive feature of MSR is that it is myopically incentive compatible: it is optimal for traders to report their true beliefs about the likelihood of an event outcome provided that they ignore the impact of their reports on the profit they might garner from future trades. In this paper, we analyze non-myopic strategies and examine what information structures lead to truthful betting by traders. Specifically, we analyze the behavior of risk-neutral traders with incomplete information playing in a dynamic game. We consider finite-stage and infinite-stage game models. For each model, we study the logarithmic market scoring rule (LMSR) with two different information structures: conditionally independent signals and (unconditionally) independent signals. In the finite-stage model, when signals of traders are independent conditional on the state of the world, truthful betting is a Perfect Bayesian Equilibrium (PBE). Moreover, it is the unique Weak Perfect Bayesian Equilibrium (WPBE) of the game. In contrast, when signals of traders are unconditionally independent, truthful betting is not a WPBE. In the infinite-stage model with unconditionally independent signals, there does not exist an equilibrium in which all information is revealed in a finite amount of time. We propose a simple discounted market scoring rule that reduces the opportunity for bluffing strategies. We show that in any WPBE for the infinite-stage market with discounting, the market price converges to the fully-revealing price, and the rate of convergence can be bounded in terms of the discounting parameter. When signals are conditionally independent, truthful betting is the unique WPBE for the infinite-stage market with and without discounting.Engineering and Applied Science

Early surgery for superficial supratentorial spontaneous intracerebral hemorrhage : a Finnish Intensive Care Consortium study

Background The benefits of early surgery in cases of superficial supratentorial spontaneous intracerebral hemorrhage (ICH) are unclear. This study aimed to assess the association between early ICH surgery and outcome, as well as the cost-effectiveness of early ICH surgery. Methods We conducted a retrospective, register-based multicenter study that included all patients who had been treated for supratentorial spontaneous ICH in four tertiary intensive care units in Finland between 2003 and 2013. To be included, patients needed to have experienced supratentorial ICHs that were 10-100 cm(3)and located within 10 mm of the cortex. We used a multivariable analysis, adjusting for the severity of the illness and the probability of surgical treatment, to assess the independent association between early ICH surgery (Peer reviewe