MAKE-OR-BUY THEORIES: WHERE DO WE STAND?

The aim of this paper is to discuss the state-of-the art and the directions for research on the make-orbuy problem. After thirty years of research efforts, we now have numerous contributions explaining different aspects of the nature and existence of the firm. The search for a unified theory, however, still remains, at a theoretical level, a challenge. The task is not easy, perhaps because the theory of the firm develops along two different strands, one analyzing the factors influencing the boundaries, and the other one relating to the internal structure; or because, even inside the same research strand, it is not really easy to grasp the similarities and differences between contributions that have followed one another in rapid succession over the last few years. This paper examines the theories concerning the make-or-buy problem, focusing on recent contributions that have tried to develop a unified framework and emphasizes the role of incomplete contracts as a common and significant trait of the theories discussed

Stock market conditions and monetary policy in an DSGE model for the US

This paper investigates the relationship between stock market fluctuations and monetary policy in a DSGE model for the US economy. We initially adopt a framework in which fluctuations in householdsâ financial wealth are allowed â but not required â to influence current consumption. This is due to interaction in the financial markets between long-time traders holding wealth accumulated over time and zero-wealth newcomers. Importantly, we introduce nominal wage stickiness to induce pro-cyclicality in real dividends. Additional nominal and real frictions are modeled to capture the pervasive macroeconomic persistence of the observables used to estimate our model. We fit our model to US post-WWII data and report three main results. First, the data strongly support a significant impact of stock prices on real activity and business cycles. Second, our estimates also identify a significant and counteractive Fed response to stock-price fluctuations. Third, we derive from our model a microfounded measure of financial slack â the stock-price gap â which we then compare with alternative measures, currently used in empirical studies, to assess the properties of the latter for capturing the dynamic and cyclical implications of our DSGE model. The behavior of our stock-price gap is consistent with the episodes of stock-market booms and busts in the post-WWII period, as reported by independent analyses, and closely correlates with the current financial meltdown. Typically, the proxies used for financial slack, such as detrended log-indexes or growth rates, show limited capabilities of capturing the implications of our model-consistent index of financial stress. Cyclical properties of the model as well as counterfactuals regarding shocks to our measure of financial slackness and monetary policy shocks are also proposed.stock prices; monetary policy; Bayesian estimation; wealth effects

Temporal evolution of oscillating coronal loops

Context. Transverse oscillations of coronal structures are currently intensively studied to explore the associated magnetohydrodynamic wave physics and perform seismology of the local medium. Aims. We make a first attempt to measure the thermodynamic evolution of a sample of coronal loops that undergo decaying kink oscillations in response to an eruption in the corresponding active region. Methods. Using data from the six coronal wavelengths of SDO/AIA, we performed a differential emission measure (DEM) analysis of 15 coronal loops before, during, and after the eruption and oscillation. Results. We find that the emission measure, temperature, and width of the DEM distribution undergo significant variations on time scales relevant for the study of transverse oscillations. There are no clear collective trends of increases or decreases for the parameters we analysed. The strongest variations of the parameters occur during the initial perturbation of the loops, and the influence of background structures may also account for much of this variation. Conclusions. The DEM analysis of oscillating coronal loops in erupting active regions shows evidence of evolution on time scales important for the study of the oscillations. Further work is needed to separate the various observational and physical mechanisms that may be responsible for the variations in temperature, DEM distribution width, and total emission measure.Comment: Accepted in A&

PRICE DISPERSION, SEARCH COSTS AND CONSUMERS AND SELLERS HETEROGENEITY IN RETAIL FOOD MARKETS

Price dispersion, i.e. a homogeneous product sold at different prices by different sellers, is among the most replicated findings in empirical economics. The paper assesses the extent and determinants of spatial price dispersion for 14 perfectly homogeneous food products in more than 400 retailers in a market characterized by the persistence of a large number of relatively small traditional food stores, side by side large supermarkets. The extent of observed price dispersion is quite high, suggesting that monopolistic competition prevails as a result of the heterogeneity of services offered. When prices in an urban area (where the spatial concentration of sellers is much higher and consumer search costs significantly lower) have been compared with those in smaller towns and rural areas, differences in search costs and the potentially higher degree of competition did not yield lower prices; quite the contrary, they were, on average, higher for 11 of the 14 products considered. Supermarkets proved to be often, but not always, less expensive than traditional retailers, although average savings from food shopping at supermarkets were extremely low. Finally, the results of the study suggest that sellers behave differently in their pricing strategies; these differences emerge both at the firm level, and for supermarkets within the same chain. The fact that products considered were homogeneous, purchases frequently repeated, the number of sellers large, and search costs relatively low, did not suffice to keep price dispersion low. From the results presented in the paper, it is clear that what is important in explaining price dispersion is the contemporaneous heterogeneity of retailers (in terms of services) and consumers (in terms of search and shopping preferences), which makes it possible for a monopolistic competition structure of the market to emerge and for small traditional food retailers to remain in business.Price dispersion, Retail pricing, Food markets

Second-Order Approximation of Dynamic Models with Time-Varying Risk

This paper provides first and second-order approximation methods for the solution of nonlinear dynamic stochastic models in which the exogenous state variables follow conditionally-linear stochastic processes displaying time-varying risk. The first-order approximation is consistent with a conditionally-linear model in which risk is still timevarying but has no distinct role - separated from the primitive stochastic disturbances - in influencing the endogenous variables. The second-order approximation of the solution, instead, is sufficient to get this role. Moreover, risk premia, evaluated using only a first-order approximation of the solution, will be also time varying.stochastic volatility, second order approximation