No abstract

It is common in the trade literature to use iceberg transport costs to represent both tariffs and shipping costs alike. However, in models with monopolistic competition these are not identical trade restrictions. This difference is driven by how the two costs affect the extensive margin. We illustrate these differences in a gravity model. We show theoretically that trade flows are more elastic with respect to tariffs than transport costs and find a linear relationship between the elasticities with respect to tariffs, iceberg transport costs, and fixed market costs. We empirically validate these results using data on US product-level imports.

There has been great focus in the recent trade theory literature on the introduction of firm heterogeneity into trade models. This introduction has highlighted the importance of the entry/exit decision of firms in response to changes in trade barriers. However, it is typical in many of these models to use iceberg transport costs as a general form of trade barriers that can be interchangeable with ad valorem tariffs. I show that this is not always an appropriate conclusion. Specifically, I illustrate that profit for an exporter is more elastic in response to tariffs than iceberg transport costs, which has implications for total product variety. One such implication is the possibility for there to be an anti -variety effect associated with lower transport costs while there also being a pro-variety effect associated with lower tariffs.JEL classification: F10; F13; F15

Mobility assessment and prediction continues to be an important and active area of research for planetary rovers, with the need illustrated by multiple examples of high slip events experienced by rovers on Mars. Despite slip versus slope being one of the strongest and most broadly used relationships in mobility prediction, this relationship is nonetheless far from precisely predictable. Although the literature has made significant advances in the predictability of average mobility, the other key related aspect of the problem is the risk caused by edge cases. A key contribution of this study is a metric for explicitly assessing mobility risk based on data-driven nonparametric slip versus slope relationships. The data-driven approach is meant to address limitations of past model-based approaches. The metric is informed by past work in terramechanics relating drawbar pull (i.e., net traction) to slip: High slip fraction (HSF), defined as the proportion of slip data points above 20%. Another contribution is a low complexity mobility prediction framework, the autonomous soil assessment system. Field tests demonstrate that, for sand and gravel, rover trafficability becomes nonlinear and highly variable above the 20% slip threshold.HSF is shown to be a useful metric for categorizing rover-terrain interactions into low, medium, or high risk, correctly and consistently. Furthermore, the metric is shown to be useful for early detection of potentially hazardous changes in roverterrain conditions. The combination of HSF with an appropriately sized queue structure for modeling slip versus slope enables an appropriate balance between responsiveness and stability. K E Y W O R D S mobility prediction, planetary robotics, rover slip

Since Baier and Bergstrand (2004) there has been a focus on empirically testing the economic determinants of signing a free trade agreement (FTA). However, FTAs do not imply an agreement on services; a separate economic integration (EIA) is needed. As trade in services is one of the fastest growing sectors of the global economy, it is important to pay special attention to these agreements. We use the methodology of Baier and Bergstrand (2004) to investigate di¤erences in the determinants of signing an agreement on goods trade and services trade. In addition to the standard economic variables, we include variables for skilled/unskilled labor, and political stability. We …nd in general, qualitative similarities (though di¤erent magnitudes) and some robust speci…c di¤erences.JEL classi…cation: F14, F15.