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Motivated by empirical evidence I uncover on the dynamics of French firms' exports, I offer a novel theory of trade frictions. Firms export only into markets where they have a contact. They search directly for new trading partners, but also use their existing network of contacts to search remotely for new partners. I characterize the dynamic formation of an international network of exporters in this model. Structurally, I estimate this model on French data and confirm its predictions regarding the distribution of the number of foreign markets accessed by exporters and the geographic distribution of exports.

The gravity equation in international trade states that bilateral exports are proportional to economic size and inversely proportional to geographic distance. While the role of size is well understood, that of distance remains mysterious. I offer an explanation for the role of distance: If (i) the distribution of firm sizes is Pareto, (ii) the average squared distance of a firm’s exports is an increasing power function of its size, and (iii) a parameter restriction holds, then the distance elasticity of trade is constant for long distances. When the firm size distribution follows Zipf’s law, trade is inversely proportional to distance.

By considering a model with identical firms, Krugman (1980) predicts that a higher elasticity of substitution between goods magnifies the impact of trade barriers on trade flows. In this paper, I introduce firm heterogeneity in a simple model of international trade. I prove that the extensive margin and the intensive margin are affected by the elasticity of substitution in exact opposite directions. When the distribution of productivity across firms is Pareto, the predictions of the Krugman model with representative firms are overturned: the impact of trade barriers on trade flows is dampened by the elasticity of substitution, and not magnified. (JEL F12, F13)

What is the impact of real estate prices on corporate investment? In the presence of financing frictions, firms use pledgeable assets as collateral to finance new projects. Through this collateral channel, shocks to the value of real estate can have a large impact on aggregate investment. To compute the sensitivity of investment to collateral value, we use local variations in real estate prices as shocks to the collateral value of firms that own real estate. Over the 1993-2007 period, the representative US corporation invests $0.06 out of each $1 of collateral.

We use 130 years of data on historical migrations to the U.S. to show a causal effect of the ancestry composition of U.S. counties on foreign direct investment (FDI) sent and received by local firms. To isolate the causal effect of ancestry on FDI, we build a simple reduced-form model of migrations: Migrations from a foreign country to a U.S. county at a given time depend on (1) a push factor, causing emigration from that foreign country to the entire U.S., and (2) a pull factor, causing immigration from all origins into that U.S. county. The interaction between time-series variation in origin-specific push factors and destination-specific pull factors generates quasi-random variation in the allocation of migrants across U.S. counties. We find that doubling the number of residents with ancestry from a given foreign country relative to the mean increases the probability that at least one local firm engages in FDI with that country by 4 percentage points. We present evidence that this effect is primarily driven by a reduction in information frictions, and not by better contract enforcement, taste similarities, or a convergence in factor endowments.

Motivated by empirical evidence I uncover on the dynamics of French firms’ exports, I offer a novel theory of trade frictions. Firms export only into markets where they have a contact. They search directly for new trading partners, but also use their existing network of contacts to search remotely for new partners. I characterize the dynamic formation of an international network of exporters in this model. Structurally, I estimate this model on French data and confirm its predictions regarding the distribution of the number of foreign markets accessed by exporters and the geographic distribution of exports.

We analyze a large data set of commercial records produced by Assyrian merchants in the nineteenth century BCE. Using the information from these records, we estimate a structural gravity model of long-distance trade in the Bronze Age. We use our structural gravity model to locate lost ancient cities. In many cases, our estimates confirm the conjectures of historians who follow different methodologies. In some instances, our estimates confirm one conjecture against others. We also structurally estimate ancient city sizes and offer evidence in support of the hypothesis that large cities tend to emerge at the intersections of natural transport routes, as dictated by topography. Finally, we document persistent patterns in the distribution of city sizes across four millennia, find a distance elasticity of trade in the Bronze Age close to modern estimates, and show suggestive evidence that the distribution of ancient city sizes, inferred from trade data, is well approximated by Zipf’s law.

There is a subgroup of patients with type 2 diabetes (T2D) in whom traditional treatment does not work well. Traditional management of T2D does not address the autoimmune component seen in a subgroup of patients with T2D. We sought to evaluate the effectiveness of using a personalized functional medicine (PFM) approach to managing T2D. Patient files from 2010 to 2015 were culled for patients previously diagnosed with T2D and their deidentified data regarding medications and T2D biomarker test results were compiled. A total of 35 patients were contacted for permission to use their deidentified data for the purposes of this article. Of 35 patients, 11 provided written consent. All participants had entered a single, private, integrative medicine clinic based in Maryland, USA. The patient group consisted of 5 women and 6 men; age 50 to 77 years. Each patient was taking an antidiabetic medication and had reached a plateau in recovery, or wanted to reduce their medication intake. Allopathic physicians were retained by patients undergoing PFM treatment. After a thorough intake history was completed, necessary specimens were collected for analysis. Once test results were reviewed to identify nutrient deficiencies, intestinal dysbiosis, hormone imbalances, chemical burden and food immune reactivities, a personalized plan was developed for each individual patient. Each patient was retested appropriately during treatment. Treatment lasted from 2 to 10 months based on the patients' goals. The effectiveness of the PFM approach was measured by the reduction in medication needed to manage T2D and improvement in T2D biomarkers. At the end of PFM treatment, 6 patients were completely off T2D-related medications, and 5 had their doses reduced by 50%. Diabetes biomarkers improved: glucose decreased by an average of 78.36 mg/dL and hemoglobin A1c (HbA1c) was lowered by an average of 2.71%. In individuals not well-managed using traditional protocols, the PFM approach should be considered as an adjunct therapy.

This essay is an analysis of Chapter 2 of Part II of Being and Time by Martin Heidegger, concerning the theme of the call of conscience as a call of care. It looks first at the concepts and questions posed in the preceding chapters and demonstrates how Heidegger discovers a phenomenological dilemma that only the call of conscience can resolve. It then analyzes Heidegger’s theory of the call of conscience and the role it plays in bringing Dasein back to the subject of its cares and to the unique situation in which it finds itself as a being thrown into a particular time and place. It looks into the ways in which it “speaks” in the mode of silence, how it only discloses “guilty” to Dasein and how it inevitably brings Dasein to the subject of its care. A special focus is placed upon the phenomenological experience of the call as presented in the text and how that relates both to Dasein’s potentiality-for-Being and Being-with others. This essay aims to show that Heidegger’s treatment of conscience is a new contribution to the question of Being that has never been fully considered before and one that has significant ramifications for philosophy in general and phenomenology in particular.