Financial Innovation and the Transactions Demand for Cash

We document cash management patterns for households that are at odds with the predictions of deterministic inventory models that abstract from precautionary motives. We extend the Baumol-Tobin cash inventory model to a dynamic environment that allows for the possibility of withdrawing cash at random times at a low cost. This modification introduces a precautionary motive for holding cash and naturally captures developments in withdrawal technology, such as the increasing diffusion of bank branches and ATM terminals. We characterize the solution of the model and show that qualitatively it is able to reproduce the empirical patterns. Estimating the structural parameters we show that the model quantitatively accounts for key features of the data. The estimates are used to quantify the expenditure and interest rate elasticity of money demand, the impact of financial innovation on money demand, the welfare cost of inflation, the gains of disinflation and the benefit of ATM ownership.

Persistent Liquidity Effects and Long Run Money Demand

We present a monetary model in the presence of segmented asset markets that implies a persistent fall in interest rates after a once and for all increase in liquidity. The gradual propagation mechanism produced by our model is novel in the literature. We provide an analytical characterization of this mechanism, showing that the magnitude of the liquidity effect on impact, and its persistence, depend on the ratio of two parameters: the long-run interest rate elasticity of money demand and the intertemporal substitution elasticity. At the same time, the model has completely classical long-run predictions, featuring quantity theoretic and Fisherian properties. The model simultaneously explains the short-run “instability” of money demand estimates as-well-as the stability of long-run interest-elastic money demand.

General Equilibrium Analysis of the Eaton-Kortum Model of International Trade

We study a variation of the Eaton-Kortum model, a competitive, constant-returns-to-scale multicountry Ricardian model of trade. We establish existence and uniqueness of an equilibrium with balanced trade where each country imposes an import tariff. We analyze the determinants of the cross-country distribution of trade volumes, such as size, tariffs and distance, and compare a calibrated version of the model with data for the largest 60 economies. We use the calibrated model to estimate the gains of a world-wide trade elimination of tariffs, using the theory to explain the magnitude of the gains as well as the differential effect arising from cross-country differences in pre-liberalization of tariffs levels and country size.

Interest rates and inflation

Monetary policy ; Interest rates ; Inflation (Finance)

Durable consumption and asset management with transaction and observation costs

The empirical evidence on rational inattention lags far behind the theoretical developments: micro evidence on the most immediate consequence of observation costs − the infrequent observation of state variables − is not available in standard datasets. We contribute to filling the gap with two novel household surveys that record the frequency with which investors observe the value of their financial investments, as well as the frequency with which they trade in financial assets and durable goods. We use these data to test some predictions of existing models and show that to match the patterns in the data we need to modify these models by shifting the focus from non-durable to durable consumption. The model we develop features both observation and transaction costs and implies a mixture of time-dependent and state-dependent rules, where the importance of each rule depends on the ratio of the observation to the transaction cost. Numerical simulations show that the model can produce frequency of portfolio observations and asset trading comparable to that of the median investor (about 4 and 0.4 per year, respectively) with small observation costs (about 1 basis point of financial wealth) and larger transaction costs (about 30 basis points of financial wealth). In spite of its small size the observation cost gives rise to infrequent information gathering (between monthly and quarterly). A quantitative assessment of the relevance of the observation costs shows that the behavior of investors is essentially unchanged compared to the one produced by a model with transaction but no observation cost. We test a novel prediction of the model on the relationship between assets trades and durable-goods trades and find that it is aligned with the data.

Optimal price setting with observation and menu costs

We model the optimal price setting problem of a firm in the presence of both information and menu costs. In this problem the firm optimally decides when to collect costly information on the adequacy of its price, an activity which we refer to as a price "review". Upon each review, the firm chooses whether to adjust its price, subject to a menu cost, and when to conduct the next price review. This behavior is consistent with recent survey evidence documenting that firms revise prices infrequently and that only a few price revisions yield a price adjustment. The goal of the paper is to study how the firm's choices map into several observable statistics, depending on the level and relative magnitude of the information vs the menu cost. The observable statistics are: the frequency of price reviews, the frequency of price adjustments, the size-distribution of price adjustments, and the shape of the hazard rate of price adjustments. We provide an analytical characterization of the firm decisions and a mapping from the structural parameters to the observable statistics. We compare these statistics with the ones obtained for the models with only one type of cost. The predictions of the model can, with suitable data, be used to quantify the importance of the menu cost vs. the information cost. We also consider a version of the model where several price adjustment are allowed between observations, a form of price plans or indexation. We find that no indexation is optimal for small inflation rates. Hard-copy subscribers may access the tables for this paper here .

Models of Idea Flows

This paper introduces several variations of the Eaton and Kortum (1999) model of technological change and characterizes their long run implications. Both exogenous and endogenous growth examples are studied.

Mixing of Non-Newtonian Fluids in Steadily Forced Systems

We investigate mixing in a viscoelastic and shear-thinning fluid—a very common combination in polymers and suspensions. We find that competition between elastic and viscous forces generates self-similar mixing, lobe transport, and other characteristics of chaos. The mechanism by which chaos is produced is evaluated both in experiments and in a simple model. We find that chaotic flow is generated by spontaneous oscillations, the magnitude and frequency of which govern the extent of chaos and mixing

Treatment with removable prosthesis in hypohidrotic ectodermal dysplasia : a clinical case

Ectodermal dysplasias form part of a wide range of syndromes presenting abnormal development of two or more tissues derived from the ectoderm. Hypohidrotic ectodermal dysplasia is a congenital syndrome, characterized by hypotrichosis (hair is sparse, fine and weak; anomalies in the skin and nails), hypohidrosis (due to the paucity of sweat glands which in turn gives rise to sweat disorders) and hypodontia (partial, and occasionally total, absence of primary and/or permanent dentition). A case of a child with hypohidrotic ectodermal dysplasia with oligodontia and marked resorption of the maxillary and mandibular alveolar ridges is presented. A prosthetic rehabilitation in the form of a removable acrylic prosthesis was made, achieving excellent esthetics, functionality and adaptation, thanks to which a considerable improvement in self-esteem has been obtained