In November 2014, OPEC announced a new strategy geared towards improving its market share. Oil-market analysts interpreted this as an attempt to squeeze higher-cost producers, notably US shale oil, out of the market. Over the next year, crude oil prices crashed, with large repercussions for the global economy. We present a simple equilibrium model that explains the fundamental market factors that can rationalize such a "regime switch" by OPEC: (i) the growth of US shale oil production; (ii) the slowdown of global oil demand; (iii) reduced cohesiveness of the OPEC cartel; and (iv) production ramp-ups in other non-OPEC countries; while (v) reductions in US shale costs act against these factors. We show that these qualitative predictions are broadly consistent with oil market developments during 2014-15. The model is calibrated to oil market data; it predicts accommodation up to 2014 and a market-share strategy thereafter, and explains large oil-price swings as well as realistically high levels of OPEC output.

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The mandate of ASA Working Group S12/WG11 has been to develop ''laboratory and/or field procedure͑s͒ that yield useful estimates of field performance'' of hearing protection devices ͑HPDs͒. A real-ear attenuation at threshold procedure was selected, devised, tested via an interlaboratory study, and incorporated into a draft standard that was approved in 1997 ͓J. D. Royster et al., ''Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise,'' J. Acoust. Soc. Am. 99, 1506-1526 ͑1996͒; ANSI S12.6-1997, ''American National Standard Methods for Measuring Real-Ear Attenuation of Hearing Protectors'' ͑American National Standards Institute, New York, 1997͔͒. The real-world estimation procedure utilizes a subject-fit methodology with listeners who are audiometrically proficient, but inexperienced in the use of HPDs. A key factor in the decision to utilize the subject-fit method was an evaluation of the representativeness of the laboratory data vis-à-vis attenuation values achieved by workers in practice. Twenty-two field studies were reviewed to develop a data base for comparison purposes. Results indicated that laboratory subject-fit attenuation values were typically equivalent to or greater than the field attenuation values, and yielded a better estimate of those values than did a͒ This paper is the last of three parts of a body of work that represents the research and analyses of S12/WG11 in conjunction with the development of ANSI S12.6-1997. Part I appeared in 1996 in J. Acoust. Soc. Am. 99, 1506-1526 ͑1996͒. It referenced two succeeding parts, one of which Part II is still in press and hence will appear out of chronological order. Additionally the advance citation of this paper in Part I, listed the first two authors in the reverse order from that which appears above. b͒ ''Selected research articles'' are ones chosen occasionally by the Editor-in-Chief that are judged ͑a͒ to have a subject of wide acoustical interest, and ͑b͒ to be written for understanding by broad acoustical readership.665 665

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This paper describes research conducted by Working Group 11 of Accredited Standards Committee S12, Noise, to develop procedures to estimate the field performance of hearing protection devices ͑HPDs͒. Current standardized test methods overestimate the attenuation achieved by workers in everyday use on the job. The goal was to approximate the amount of attenuation that can be achieved by noise-exposed populations in well-managed real-world hearing conservation programs, while maintaining acceptable interlaboratory measurement variability. S12/WG11 designed two new laboratory-based protocols for measuring real-ear attenuation at threshold, with explicit procedures for subject selection, training, supervision, and HPD fitting. After pilot-testing, S12/WG11 conducted a full-scale study of three types of earplugs and one earmuff tested by four independent laboratories using both protocols. The protocol designated as ''subject-fit'' assessed the attenuation achieved by subjects who were experienced in threshold audiometry, but naive with respect to the use of hearing protection, when they fit HPDs by following manufacturers' instructions without any experimenter assistance. The attenuation results from the subject-fit method corresponded more closely to real-world data than results from the other protocol tested, which allowed the experimenter to coach subjects in HPD use. Comparisons of interlaboratory measurement variability for the subject-fit procedure to previous interlaboratory studies using other protocols indicated that the measurements with the new procedure are at least as reproducible as those obtained with existing standardized methods. Therefore, the subject-fit protocol was selected for consideration for use in

We present a gravity model that accounts for multilateral resistance, firm heterogeneity and countryselection into trade, while accommodating asymmetries in trade flows. A new equation for the proportion of exporting firms takes a gravity form, such that the extensive margin is also affected by multilateral resistance. We develop Taylor approximated multilateral resistance terms with which to capture the comparative static effects of changes in trade costs. For isolated bilateral changes in trade frictions, multilateral resistance effects are small for most countries. However, if all countries reduce their trade frictions, the impact of multilateral resistance is so strong that bilateral trade falls in most cases, despite the larger trade elasticities implied by firm heterogeneity. As a consequence, the worldwide trade response, though positive, is much lower.

Better international logistics raise a developing country's exports, but the magnitude of the effect depends on the country's size. We apply a gravity model that accounts for firm heterogeneity and multilateral resistance to an international logistics index. A one standard deviation improvement in logistics is equivalent to a 14% reduction in distance. An average‐sized developing country would raise exports by approximately 36%. Most of the countries are much smaller than average, so the typical effect is 8%. This difference is chiefly due to the dampening effect of multilateral resistance, which is more important for small countries.

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