We present a new model of multi-product firms (MPFs) and flexible manufacturing, and explore its implications in partial and general oligopolistic equilibrium. Globalization affects the scale and ...scope (or intensive margin and intra-firm extensive margin) of MPFs through a competition effect and a demand effect. The model highlights a new source of gains from trade: productivity increases as firms become "leaner and meaner", concentrating on their core competence; but also a new source of losses from trade: product variety may fall. Our results also hold under free entry, which allows in addition for adjustment along the traditional inter-firm extensive margin.
This paper presents a new model of oligopoly in general equilibrium and explores its implications for positive and normative aspects of international trade. Assuming “continuum–Pollak” preferences, ...the model allows for consistent aggregation over a continuum of sectors, in each of which a small number of home and foreign firms engage in Cournot competition. I show how competitive advantage interacts with comparative advantage to determine resource allocation and, specializing to continuum–quadratic preferences, I explore the model's implications for the gains from trade, for the distribution of income between wages and profits, and for production and trade patterns in a two‐country world.
There are multiple J.R. Smallwoods, but the aspiring and ambitious figure presented in this biography stands apart. Melvin Baker and Peter Neary use the largely untapped sources of Smallwood's own ...papers and his extensive journalistic writing to add a documentary basis to what is known or conjectured about the first five decades of Smallwood's remarkable life, both public and private.
Selection Effects with Heterogeneous Firms Mrázová, Monika; Neary, J Peter
Journal of the European Economic Association,
08/2019, Letnik:
17, Številka:
4
Journal Article
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Abstract
We characterize how firms select between alternative ways of serving a market. “First-order” selection effects, whether firms enter or not, are extremely robust. “Second-order” ones, how ...firms serve a market conditional on entry, are much less so: more efficient firms select the entry mode with lower market-access costs if firms’ maximum profits are supermodular in production and market-access costs, but not necessarily otherwise. We derive microfoundations for supermodularity in a range of canonical models. Notable exceptions include horizontal and vertical FDI with “subconvex” demands (i.e., less convex than CES), fixed costs that increase with productivity, and R&D with threshold effects.
Abstract
Gravity as both fact and theory is one of the great success stories of recent research on international trade, and has featured prominently in the policy debate over Brexit. We first review ...the facts, noting the overwhelming evidence that trade tends to fall with distance. We then introduce some expository tools for understanding constant-elasticity-of-substitution theories of gravity as a simple general-equilibrium system. Next, we point out some anomalies with the theory: mounting evidence against constant trade elasticities, and implausible predictions for bilateral trade balances. Finally, we sketch an approach based on subconvex gravity as a promising direction to resolving them.
We develop a new model of multi-product firms which invest to improve the perceived quality of both their individual products and their brand. Because of flexible manufacturing, products closer to ...firms' core competence have lower costs, so firms produce more of them, and also have higher incentives to invest in their quality. These two effects have opposite implications for the profile of prices. Mexican data provide robust confirmation of the model's key prediction: firms in differentiated-good sectors exhibit quality-based competence (prices fall with distance from core competence), but export sales of firms in non-differentiated-good sectors exhibit the opposite pattern.
•We develop a new model of multi-product firms which invest in quality.•Firms' core competence products have higher output and quality.•These two effects have opposite implications for the profile of prices.•Mexican data provide robust confirmation of the model's key prediction.•Only firms in differentiated-good sectors exhibit quality-based competence.
Introduction
Despite increasing endorsement of near-infrared perfusion assessment using indocyanine green (ICG) during colorectal surgery, little work has yet been done regarding learning curve and ...interobserver variation most especially on surgical video reflective of real-world usage.
Methods
Surgeons with established expertise in ICG usage were invited to participate in the study along with others without such experience including trainees. All participants completed an opinion questionnaire and interpreted video presentations of fluorescence angiograms in a variety of colorectal case scenarios. An interactive video platform (Mindstamp) enabled dynamic annotation. Statistical analysis of data was performed using Kruskal–Wallis and Mann–Whitney testing as well as Intraclass Correlation Coefficients and Fleiss Multi-rater Kappa Scoring.
Results
Forty participants (six experts) completed questionnaire data and provided judgement of 14 videos (nine showing proximal colonic transection site perfusion, four showing completed anastomoses and one an acutely strangulated bowel). 70% felt > 10 cases were needed for competency in use with the majority of experts advocating > 50 (
p
< 0.05). Overall agreement among experts was “good” for videos showing colonic transection perfusion (versus “moderate” among in-experts) with experts clustering more distally. In contrast, there was no interpretation concordance among experts or in-experts when judging ICG perfusion sufficiency on a yes/no basis.
Conclusion
Significant experience is recommended before reliance on ICG perfusion angiograms. ICG fluorescence assessment is prone to variable interpretation and influenced by experience and, perhaps, knowledge of preassessment operative steps suggesting a role for objective flow analysis with artificial intelligence methods as the next phase of this technology.
We show that relaxing the assumption of CES preferences in monopolistic competition has surprising implications when trade is restricted. Integrated and segmented markets behave differently, the ...latter typically exhibiting reciprocal dumping. Globalization and lower trade costs have different effects. The former reduces spending on all existing varieties, the latter switches spending from home to imported varieties; when demands are less convex than CES, globalization raises whereas lower trade costs reduce firm output. Finally, calibrating gains from trade is harder. Many more parameters are needed, while import demand elasticities typically overestimate the true elasticities, and so underestimate the gains from trade.
Introduction
Indocyanine green (ICG) quantification and assessment by machine learning (ML) could discriminate tissue types through perfusion characterisation, including delineation of malignancy. ...Here, we detail the important challenges overcome before effective clinical validation of such capability in a prospective patient series of quantitative fluorescence angiograms regarding primary and secondary colorectal neoplasia.
Methods
ICG perfusion videos from 50 patients (37 with benign (13) and malignant (24) rectal tumours and 13 with colorectal liver metastases) of between 2- and 15-min duration following intravenously administered ICG were formally studied (clinicaltrials.gov: NCT04220242). Video quality with respect to interpretative ML reliability was studied observing practical, technical and technological aspects of fluorescence signal acquisition. Investigated parameters included ICG dosing and administration, distance–intensity fluorescent signal variation, tissue and camera movement (including real-time camera tracking) as well as sampling issues with user-selected digital tissue biopsy. Attenuating strategies for the identified problems were developed, applied and evaluated. ML methods to classify extracted data, including datasets with interrupted time-series lengths with inference simulated data were also evaluated.
Results
Definable, remediable challenges arose across both rectal and liver cohorts. Varying ICG dose by tissue type was identified as an important feature of real-time fluorescence quantification. Multi-region sampling within a lesion mitigated representation issues whilst distance–intensity relationships, as well as movement-instability issues, were demonstrated and ameliorated with post-processing techniques including normalisation and smoothing of extracted time–fluorescence curves. ML methods (automated feature extraction and classification) enabled ML algorithms glean excellent pathological categorisation results (AUC-ROC > 0.9, 37 rectal lesions) with imputation proving a robust method of compensation for interrupted time-series data with duration discrepancies.
Conclusion
Purposeful clinical and data-processing protocols enable powerful pathological characterisation with existing clinical systems. Video analysis as shown can inform iterative and definitive clinical validation studies on how to close the translation gap between research applications and real-world, real-time clinical utility.
Not So Demanding Mrázová, Monika; Neary, J. Peter
The American economic review,
12/2017, Letnik:
107, Številka:
12
Journal Article
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We show that any well-behaved demand function can be represented by its “demand manifold,” a smooth curve that relates the elasticity and convexity of demand. This manifold is a sufficient statistic ...for many comparative statics questions; leads naturally to characterizations of new families of demand functions that nest most of those used in applied economics; and connects assumptions about demand structure with firm behavior and economic performance. In particular, the demand manifold leads to new insights about industry adjustment with heterogeneous firms, and can be empirically estimated to provide a quantitative framework for measuring the effects of globalization.
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