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AbstractWe quantify the magnitude of market segmentation in US consumer market and explore the underlying factors behind this segmentation, using a quarterly panel of retail prices for 45 products in 48 US cities from 1985 to 2009. The extent of market segmentation is estimated using city‐pair price differences within the framework of both linear autoregressive (AR) and nonlinear threshold autoregressive (TAR) models. We find that the magnitude of market segmentation varies from one product to another, but even more across city pairs in each product. Contrary to a widespread perception, market segmentation within the US is not necessarily larger for non‐tradable services compared to tradable goods. We identify potential drivers of market segmentation by relating the cross‐city and cross‐product variations of market segmentation to location‐specific and product‐specific characteristics—distance, relative city sizes, differences in wage and rent, type of product and proximity to marketplace. Distance, which captures more than transport costs, turns out to be the most salient factor even after controlling for a range of other potential factors. The effect of distance, however, varies substantially across products, with perishable products and locally produced products showing larger distance effect on market segmentation. We find that the magnitude of market segmentation has been somewhat stable during the sample period, but intercity price differences have become more sensitive to distance over time in many products under study.

Vector autoregressive (VAR) models are among the most widely used econometric tools in the fields of macroeconomics and financial economics. Much of what we know about the response of the economy to macroeconomic shocks and about how various shocks have contributed to the evolution of macroeconomic and financial aggregates is based on VAR models. VAR models also have been used successfully for economic and business forecasting, for modeling risk and volatility, and for the construction of forecast scenarios. Since the introduction of VAR models by C.A. Sims in 1980, the VAR methodology has continuously evolved. Even today important extensions and reinterpretations of the VAR framework are being developed. Examples include VAR models for mixed-frequency data, VAR models as approximations to DSGE models, factor-augmented VAR models, new tools for the identification of structural shocks in VAR models, panel VAR approaches, and time-varying parameter VAR models. This volume collects contributions from some of the leading VAR experts in the world on VAR methods and applications. Each paper highlights and synthesizes a new development in this literature in a way that is accessible to practitioners, to graduate students, and to readers in other fields.

Low-temperature plasma physics and technology are diverse and interdisciplinary fields. The plasma parameters can span many orders of magnitude and applications are found in quite different areas of daily life and industrial production. As a consequence, the trends in research, science and technology are difficult to follow and it is not easy to identify the major challenges of the field and their many sub-fields. Even for experts the road to the future is sometimes lost in the mist. Journal of Physics D: Applied Physics is addressing this need for clarity and thus providing guidance to the field by this special Review article, The 2012 Plasma Roadmap. Although roadmaps are common in the microelectronic industry and other fields of research and development, constructing a roadmap for the field of low-temperature plasmas is perhaps a unique undertaking. Realizing the difficulty of this task for any individual, the plasma section of the Journal of Physics D Board decided to meet the challenge of developing a roadmap through an unusual and novel concept. The roadmap was divided into 16 formalized short subsections each addressing a particular key topic. For each topic a renowned expert in the sub-field was invited to express his/her individual visions on the status, current and future challenges, and to identify advances in science and technology required to meet these challenges. Together these contributions form a detailed snapshot of the current state of the art which clearly shows the lifelines of the field and the challenges ahead. Novel technologies, fresh ideas and concepts, and new applications discussed by our authors demonstrate that the road to the future is wide and far reaching. We hope that this special plasma science and technology roadmap will provide guidance for colleagues, funding agencies and government institutions. If successful in doing so, the roadmap will be periodically updated to continue to help in guiding the field. © 2012 IOP Publishing Ltd.