Supplier Search and Re-matching in Global Sourcing - Theory and Evidence from China

In this paper, we consider a dynamic search-and-matching problem of a firm with its intermediate input supplier. In our model, a headquarter currently matched with a supplier, has an interest to find and collaborate with a more efficient partner. However, supplier switching through search and re-matching is costly. Given this trade-off between the fixed costs and the expected gains from continued search, the process will stop whenever the headquarter has found a sufficiently efficient supplier. Using firm-product-level data of fresh Chinese exporters to the United States, we obtain empirical evidence in line with the predictions of our theory. In particular, we find that the share of short-term collaborations is higher in industries with more supplier-cost dispersion, an indication of higher expected search opportunities

Proposal of a Nutritional Quality Index (NQI) to Evaluate the Nutritional Supplementation of Sportspeople

Background: Numerous supplements are used by sportspeople. They are not always appropriate for the individual or the sports activity and may do more harm than good. Vitamin and mineral supplements are unnecessary if the energy intake is sufficient to maintain body weight and derives from a diet with an adequate variety of foods. The study objectives were to evaluate the main nutrients used as supplements in sports and to propose a nutritional quality index (NQI) that enables sportspeople to optimize their use of supplements and detect and remedy possible nutritional deficits. Material and Methods: A nutritional study was performed in 485 sportspeople recruited from Centros Andaluces de Medicina del Deporte, (CAMD). All completed socio-demographic, food frequency, and lifestyle questionnaires. The nutritional quality of their diet and need for supplementation were evaluated by scoring their dietary intake with and without supplementation, yielding two NQI scores (scales of 0-21 points) for each participant. Results: A superior mean NQI score was obtained when the supplements taken by participants were not included (16. 28 (SD of 3.52)) than when they were included (15.47 (SD: 3.08)), attributable to an excessive intake of some nutrients through supplementation. Conclusions: These results indicate that sportspeople with a varied and balanced diet do not need supplements, which appear to offer no performance benefits and may pose a health risk.The authors are grateful to the Junta de Andalucía, Spain (Research Group AGR-255“Nutrition. Diet and Risk Assessment”), a collaboration agreement with the Andalusian Centres of Sports Medicine (Junta de Andalucía) and the FPU program of the Spanish Ministry of Education and Science. Study participants were recruited through the project “Nutritional and diet assessment methodologies applied to the Andalusian sportsperson in Andalusian Sports centres”, Research project FMD2010SC0071 of the Junta de Andalucía

Data for: City age and city size

Abstract of associated article: Using novel data on the foundation dates of more than 10,000 American Census places, we show that older cities in the US tend to be larger than younger ones. To take this nexus between city age and city size into account, we introduce endogenous city creation into a dynamic economic model of an urban system. Our model predicts a pattern of age-dependent urban growth that is in line with recently established empirical evidence. The size distribution that emerges in our economy delivers a close fit to different types of US data and it outperforms other suggested parametrizations. This evidence can resolve several debates and build a bridge between different views in the literature on city size distributions

Spatial frictions

The world is replete with spatial frictions. Shipping goods across cities entails trade frictions. Commuting within cities causes urban frictions. How important are these frictions in shaping the spatial economy? We develop and quantify a novel framework to address this question at three different levels: Do spatial frictions matter for the city-size distribution? Do they affect individual city sizes? Do they contribute to the productivity advantage of large cities and the toughness of competition in cities? The short answers are: no; yes; and it depends