THE ECONOMICS OF AIR TRAVEL GRAVITY MODELS*

Starting with the aggregate demand model of economics, a model of demand for intercity air travel is developed which contains the gravity model as a less general submodel. The more general model is referred to as the alternative opportunities model since it takes account of alternative destinations open to travelers, not just origin and destination as does the gravity model. The demand model approach has the virtue of providing a theoretical basis for understanding and analyzing the gravity model. The gains from treating alternative locations and demand motivation variables are a substantial increase in explanatory power over that yielded by the gravity model, the identification of statistically significant determinants of air travel, and better measurement of the coefficients of population and distance by taking account of these other variables and somewhat better forecasts. A shortcoming of procedures used here is aggregation of air trips with different purposes and thus lack of clear specification of the size of effects of different variables on different types of travel. Overcoming this difficulty must await origin-destination data listed by trip purpose.     

Political Ecologies of Global Health: Pesticide Exposure in Southwestern Ecuador's Banana Industry

Pesticide exposure in Ecuador's banana industry reflects political economic and ecological processes that interact across scales to affect human health. We use this case study to illustrate opportunities for applying political ecology of health scholarship in the burgeoning field of global health. Drawing on an historical literature review and ethnographic data collected in Ecuador's El Oro province, we present three main areas where a political ecological approach can enrich global health scholarship: perceptive characterization of multi‐scalar and ecologically entangled pathways to health outcomes; critical analysis of discursive dynamics such as competing scalar narratives; and appreciation of the environment‐linked subjectivities and emotions of people experiencing globalized health impacts. Rapprochement between these fields may also provide political ecologists with access to valuable empirical data on health outcomes, venues for engaged scholarship, and opportunities to synthesize numerous insightful case studies and discern broader patterns.     

Taken with a Grain of Salt: Experimentation and the Chemistry of Archaeological Ceramics from Xaltocan,Mexico

Neutron activation analysis (NAA) of ceramics from Xaltocan (n?=?651) displays high values for sodium and potassium and low concentrations of many transition metals and rare earth elements compared to other sites in the Basin of Mexico. Given that Xaltocan was situated on an island in the middle of a saline lake, the potential reasons for this chemical signature are diverse. On one hand, if the sodium and potassium were elevated due to some behavioral aspect of the potters, the Xaltocan chemical groups provide a glimpse at the behaviors of Xaltocan potters that permit more precise source designations. On the other hand, if this chemical fingerprint arose due to contamination in a saline post-depositional environment, the Xaltocan chemical groups would not be valid references for provenance studies. To evaluate these alternative hypotheses, we employ several lines of evidence: (1) comparison of the Xaltocan ceramics to over 5,000 NAA assays of clays and ceramics from the Basin of Mexico, (2) experimental doping of clays with water of different salinities and fired to different temperatures, (3) leaching experiments of archaeological pottery sherds (n?=?22) recovered from the site of Xaltocan, and (4) laser ablation–inductively coupled plasma–mass spectrometry of the clay and temper fraction of a small sample of Xaltocan ceramics to determine which component is responsible for the elevated sodium and potassium values. The results suggest that the high sodium and potassium values were present in the ceramic paste before firing. We then use these newly established reference groups to better understand the role of Xaltocan in the regional economy. The type of experimentation employed in this study has proven to be an important method for determining the behaviors of ancient potters and distinguishing them from post-depositional processes.     

SPATIAL COMPETITION,PRICING, AND MARKET POWER IN TRANSPORTATION: A DOMINANT FIRM MODEL*

ABSTRACT Transport firms compete over space. We develop a dominant firm model of transport services wherein one firm (the railroad) has market power, but competes in space with a competitive alternative (truck‐barge). When constrained, the dominant firm prices to “beat the competition”, which impedes efficiency when demand has some elasticity. We extend the basic model in a number of directions that include the relationship between monopoly prices and the generalized concavity of the shipper demand functions, the effects of multiple terminal markets, the role of joint production (fronthaul–backhaul markets), and the effects of capacity constraints.     

Transitions in Social Organization: A Predictive Model from Southwestern Archaeology

A number of studies from experimental psychology suggest the existence of information-processing constraints that place limits on the number of people with which an individual may simultaneously interact. The existence of such constraints means that increases in the size of a human group will push that population toward “scalar thresholds,” at which point a transformation of the social order must take place to reorganize patterns of group interaction. The model developed here incorporates ethnographic data into the scalar theory of social change in an attempt to refine the precision with which scalar thresholds may be predicted. This scalar model contributes to an understanding of social change in small- to midsized sedentary populations and provides insight into processes by which social differentiation can emerge in these societies.     

Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia

ABSTRACT

The residents of the Canary Archipelago consumed limpets since the arrival of humans ～2500 yrs. ago, and these harvested gastropods were deposited in large coastal shell middens. This work preliminarily explores shell margin oxygen isotope composition (δ¹⁸O) and body size of the black limpet (Patella candei d’Orbigny, 1840) from archaeological sites in the Canary Islands to assess possible seasonal variability and intensity of shellfish collection throughout the late Holocene. The shell margin δ¹⁸O values of 100 shells (radiocarbon dated between ～500 and ～1800 cal. yr BP) were analysed to estimate sea surface temperature (SST) at time of death. Paleotemperature estimates suggest shellfish harvesting was not year-round, and was avoided in the cooler months (when SST?<?20°C). This pattern differs from most higher latitude Mesolithic and Neolithic human groups, which gathered shellfish year-round, targeting winter more heavily. Preliminary body-size measurements suggest shell sizes have experienced a decline from aboriginal times to the present, which possibly resulted from increasing anthropogenic pressures. During aboriginal inhabitation, maximum adult shell size remained stable, suggesting that present-day harvesting practices are more intense than harvesting from aboriginal human groups. This intensive collection has likely diminished the average adult size of limpet populations in the islands by ～27%.     

The Whips of the Liberal Unionist Party in the House of Commons

This note provides the most complete list of Liberal Unionist whips in the house of commons, thus contributing to our understanding of the history of the party in parliament over the entire period of its existence from 1886 to 1912, and charts the extent of the responsibility of the party whip for the organisation of the party outside the house of commons, which peaked during the tenure of Lord Wolmer as whip from 1888 to 1892. The note concludes by observing that the division of labour regarding organisation implemented in the Conservative Party in 1911 mirrors that adopted by the Liberal Unionist Party in 1892, and that this was likely the result of Wolmer, now 2nd earl of Selborne, serving on the committee that recommended the 1911 reforms.