Capital Flows to Developing Countries: The Allocation Puzzle

The textbook neoclassical growth model predicts that countries with faster productivity growth should invest more and attract more foreign capital. We show that the allocation of capital flows across developing countries is the opposite of this prediction: capital seems to flow more to countries that invest and grow less. We then introduce wedges into the neoclassical growth model and find that one needs a saving wedge in order to explain the correlation between growth and capital flows observed in the data. We conclude with a discussion of some possible avenues for research to resolve the contradiction between the model predictions and the data.Capital Flows, Productivity, Growth

Models of Comptonization

After a rapid introduction about the models of comptonization, we present some simulations that underlines the expected capabilities of Simbol-X to constrain the presence of this process in objects like AGNs or XRB.Comment: 5 pages, 6 figures, invited talk at 'Simbol-X: the hard X-ray universe in focus', Bologna (Italy), 14-16 May, 2007. To appear in Memorie della SAI

Capital Flows to Developing Countries: the Allocation Puzzle

capital flows, emerging countries, Feldstein Horioka, neoclassical growth model, Lucas puzzle

Capital Flows to Developing Countries: The Allocation Puzzle

According to the consensus view in growth and development economics, cross country differences in per-capita income largely reflect differences in countries' total factor productivity. We argue that this view has powerful implications for patterns of capital flows: everything else equal, countries with faster productivity growth should invest more, and attract more foreign capital. We then show that the pattern of net capital flows across developing countries is not consistent with this prediction. If anything, capital seems to flow more to countries that invest and grow less. We argue that this result -- which we call the allocation puzzle -- constitutes an important challenge for economic research, and discuss some possible research avenues to solve the puzzle.

The Elusive Gains from International Financial Integration

Standard theoretical arguments tell us that countries with relatively little capital benefit from financial integration as foreign capital flows in and speeds up the process of convergence. We show in a calibrated neoclassical model that conventionally measured welfare gains from this type of convergence appear relatively limited for the typical emerging country. The welfare gain from switching from financial autarky to perfect capital mobility is roughly equivalent to a one percent permanent increase in domestic consumption for the typical emerging economy. This is negligible relative to the potential welfare gain of a take-off in domestic productivity of the magnitude observed in some of these countries.

Fast rates in learning with dependent observations

In this paper we tackle the problem of fast rates in time series forecasting from a statistical learning perspective. In a serie of papers (e.g. Meir 2000, Modha and Masry 1998, Alquier and Wintenberger 2012) it is shown that the main tools used in learning theory with iid observations can be extended to the prediction of time series. The main message of these papers is that, given a family of predictors, we are able to build a new predictor that predicts the series as well as the best predictor in the family, up to a remainder of order $1/\sqrt{n}$. It is known that this rate cannot be improved in general. In this paper, we show that in the particular case of the least square loss, and under a strong assumption on the time series (phi-mixing) the remainder is actually of order $1/n$. Thus, the optimal rate for iid variables, see e.g. Tsybakov 2003, and individual sequences, see \cite{lugosi} is, for the first time, achieved for uniformly mixing processes. We also show that our method is optimal for aggregating sparse linear combinations of predictors

Causal conditioning and instantaneous coupling in causality graphs

The paper investigates the link between Granger causality graphs recently formalized by Eichler and directed information theory developed by Massey and Kramer. We particularly insist on the implication of two notions of causality that may occur in physical systems. It is well accepted that dynamical causality is assessed by the conditional transfer entropy, a measure appearing naturally as a part of directed information. Surprisingly the notion of instantaneous causality is often overlooked, even if it was clearly understood in early works. In the bivariate case, instantaneous coupling is measured adequately by the instantaneous information exchange, a measure that supplements the transfer entropy in the decomposition of directed information. In this paper, the focus is put on the multivariate case and conditional graph modeling issues. In this framework, we show that the decomposition of directed information into the sum of transfer entropy and information exchange does not hold anymore. Nevertheless, the discussion allows to put forward the two measures as pillars for the inference of causality graphs. We illustrate this on two synthetic examples which allow us to discuss not only the theoretical concepts, but also the practical estimation issues.Comment: submitte

A Hardware Time Manager Implementation for the Xenomai Real-Time Kernel of Embedded Linux

Nowadays, the use of embedded operating systems in different embedded projects is subject to a tremendous growth. Embedded Linux is becoming one of those most popular EOSs due to its modularity, efficiency, reliability, and cost. One way to make it hard real-time is to include a real-time kernel like Xenomai. One of the key characteristics of a Real-Time Operating System (RTOS) is its ability to meet execution time deadlines deterministically. So, the more precise and flexible the time management can be, the better it can handle efficiently the determinism for different embedded applications. RTOS time precision is characterized by a specific periodic interrupt service controlled by a software time manager. The smaller the period of the interrupt, the better the precision of the RTOS, the more it overloads the CPU, and though reduces the overall efficiency of the RTOS. In this paper, we propose to drastically reduce these overheads by migrating the time management service of Xenomai into a configurable hardware component to relieve the CPU. The hardware component is implemented in a Field Programmable Gate Array coupled to the CPU. This work was achieved in a Master degree project where students could apprehend many fields of embedded systems: RTOS programming, hardware design, performance evaluation, etc.Comment: Embed With Linux (EWiLi) workshop, Lorient : France (2012