Two Ways to Rule Out the Overconsumption Paths in the Ramsey Model with Irreversible Investment

In this note I develop two approaches to rule out the overconsumption paths in the Ramsey model with irreversible capital. The ørst focuses on the multiplier of the irreversible constraint and is applied to the situation where preferences are CES and the production function is Cobb-Douglas. The second, relies on a revealed preference argument and is used to rule out overconsumption paths when the preferences are strictly concave and the initial level of per effective capital is below its steady state level.RAMSEY GROWTH MODEL; IRREVERSIBLE CAPITAL; OVERCONSUMPTION PATHS

Using Investment Data to Assess the Importance of Price Mismeasurement

This paper presents a new approach to assess the role of price mismeasurement in the productivity slowdown. I invert the firm's investment decision to identify the embodied and disembodied components of productivity growth. With a Cobb-Douglas production function, output price mismeasurement only should affect the latter. Contrary to the mismeasurement hypothesis, I find that in the Post-War period, disembodied productivity grew faster in the hard-to-measure than in the non-manufacturing easy-to-measure sectors, and that disembodied productivity slowed down less in the hard-to-measure than in the easy-to-measure sectors since the 70's. These results hold a fortiori when capital and labor are complements.INVESTMENT; PRICE MISMEASUREMENT; PRODUCTIVITY SLOWDOWN; TOTAL FACTOR PRODUCTIVITY ;EMBODIED AND DISEMBODIED PRODUCTIVITY

Medium Term Business Cycles

Over the postwar, the U.S., Europe and Japan have experienced what may be thought of as medium frequency oscillations between persistent periods of robust growth and persistent periods of relative stagnation. These medium frequency movements, further, appear to bear some relation to the high frequency volatility of output. That is, periods of stagnation are often associated with significant recessions, while persistent booms typically are either free of recessions or are interrupted only by very modest downturns. In this paper we explore the idea of medium term cycles, which we define as reflecting the sum of the high and medium frequency variation in the data. We develop a methodology for identifying these kinds of fluctuations and then show that a number of important macroeconomic time series exhibit significant medium term cycles. The cycles feature strong procyclical movements in both disembodied and embodied technological change, research & development, and the efficiency of resource utilization. We then develop a model to explain the medium term cycle that features both disembodied and embodied endogenous technological change, along with countercyclical markups and variable factor utilization. The model is able to generate medium term fluctuations in output, technological change, and resource utilization that resemble the data, with a non-technological shock as the exogenous disturbance. In particular, the model offers a unified approach to explaining both high and medium frequency variation in aggregate business activity.BUSINESS CYCLE; ENDOGENOUS TECHNOLOGICAL CHANGE.

Cross-Country Technology Adoption: Making the Theories Face the Facts.

We examine the diffusion of more than twenty technologies across twenty-three of the world ’s leading industrial economies. Our evidence covers major technology classes such as textile production, steel manufacture, communications, information technology, transportation, and electricity for the period 1788-2001. We document the common patterns observed in the diffusion of this broad range of technologies. Our results suggest a pattern of trickle-down diffusion that is remarkably robust across technologies. Most of the technologies that we consider originate in advanced economies and are adopted there first. Subsequently, they trickle down to countries that lag economically. Our panel data analysis indicates that the most important determinants of the speed at which a country adopts technologies are the country’s human capital endowment, type of government, degree of openness to trade, and adoption of predecessor technologies. We also find that the overall rate of diffusion has increased markedly since World War II because of the convergence in these variables across countries.ECONOMIC GROWTH; HISTORICAL DATA; TECHNOLOGY ADOPTION.

R&D? A Small Contribution to Productivity Growth

In this paper I calibrate the contribution of R&D investments to productivity growth. The basis for the analysis is the free entry condition. This yields a relationship between the resources devoted to R&D and the growth rate of technology. Since innovators are small, this relationship is not directly a¥ected by the size of the R&D externalities, the presence of scale effects or diminishing returns in R&D after controlling for the growth rate of output and the interest rate. The resulting contribution of R&D to productivity growth in the US is smaller than three to five tenths of one percentage point. Interestingly, this constitutes an upper bound for the case where innovators internalize the consequences of their R&D investments on the cost of conducting future innovations. From a normative perepective, this analysis implies that, if the innovation technology takes the form assumed in the literature, the actual US R&D intensity may be the socially optimal.RESEARCH AND DEVELOPMENT; PRODUCTIVITY GROWTH; TOTAL FACTOR PRODUCTIVITY

When does domestic saving matter for economic growth?

Can a country grow faster by saving more? We address this question both theoretically and empirically. In our model, growth results from innovations that allow local sectors to catch up with the frontier technology. In relatively poor countries, catching up with the frontier requires the involvement of a foreign investor, who is familiar with the frontier technology, together with effort on the part of a local bank, who can directly monitor local projects to which the technology must be adapted. In such a country, local saving matters for innovation, and therefore growth, because it allows the domestic bank to cofinance projects and thus to attract foreign investment. But in countries close to the frontier, local firms are familiar with the frontier technology, and therefore do not need to attract foreign investment to undertake an innovation project, so local saving does not matter for growth. In our empirical exploration we show that lagged savings is significantly associated with productivity growth for poor but not for rich countries. This effect operates entirely through TFP rather than through capital accumulation. Further, we show that savings is significantly associated with higher levels of FDI inflows and equipment imports and that the effect that these have on growth is significantly larger for poor countries than rich

A systematic comparison of supervised classifiers

Pattern recognition techniques have been employed in a myriad of industrial, medical, commercial and academic applications. To tackle such a diversity of data, many techniques have been devised. However, despite the long tradition of pattern recognition research, there is no technique that yields the best classification in all scenarios. Therefore, the consideration of as many as possible techniques presents itself as an fundamental practice in applications aiming at high accuracy. Typical works comparing methods either emphasize the performance of a given algorithm in validation tests or systematically compare various algorithms, assuming that the practical use of these methods is done by experts. In many occasions, however, researchers have to deal with their practical classification tasks without an in-depth knowledge about the underlying mechanisms behind parameters. Actually, the adequate choice of classifiers and parameters alike in such practical circumstances constitutes a long-standing problem and is the subject of the current paper. We carried out a study on the performance of nine well-known classifiers implemented by the Weka framework and compared the dependence of the accuracy with their configuration parameter configurations. The analysis of performance with default parameters revealed that the k-nearest neighbors method exceeds by a large margin the other methods when high dimensional datasets are considered. When other configuration of parameters were allowed, we found that it is possible to improve the quality of SVM in more than 20% even if parameters are set randomly. Taken together, the investigation conducted in this paper suggests that, apart from the SVM implementation, Weka's default configuration of parameters provides an performance close the one achieved with the optimal configuration

Orbital Symmetries of Charge Density Wave Order in YBa2Cu3O6+x

Charge density wave (CDW) order has been shown to compete and coexist with superconductivity in underdoped cuprates. Theoretical proposals for the CDW order include an unconventional $d$-symmetry form factor CDW, evidence for which has emerged from measurements, including resonant soft x-ray scattering (RSXS) in YBa$_2$Cu$_3$O$_{6+x}$ (YBCO). Here, we revisit RSXS measurements of the CDW symmetry in YBCO, using a variation in the measurement geometry to provide enhanced sensitivity to orbital symmetry. We show that the $(0\ 0.31\ L)$CDW peak measured at the Cu$L$edge is dominated by an$s$form factor rather than a$d$form factor as was reported previously. In addition, by measuring both$(0.31\ 0\ L)$and$(0\ 0.31\ L)$peaks, we identify a pronounced difference in the orbital symmetry of the CDW order along the$a$and$b$axes, with the CDW along the$a$ axis exhibiting orbital order in addition to charge order.Comment: 17 pages, 4 figures + supplementary informatio

Na2IrO3 as a spin-orbit-assisted antiferromagnetic insulator with a 340 meV gap

We study Na2IrO3 by ARPES, optics, and band structure calculations in the local-density approximation (LDA). The weak dispersion of the Ir 5d-t2g manifold highlights the importance of structural distortions and spin-orbit coupling (SO) in driving the system closer to a Mott transition. We detect an insulating gap {\Delta}_gap = 340 meV which, at variance with a Slater-type description, is already open at 300 K and does not show significant temperature dependence even across T_N ~ 15 K. An LDA analysis with the inclusion of SO and Coulomb repulsion U reveals that, while the prodromes of an underlying insulating state are already found in LDA+SO, the correct gap magnitude can only be reproduced by LDA+SO+U, with U = 3 eV. This establishes Na2IrO3 as a novel type of Mott-like correlated insulator in which Coulomb and relativistic effects have to be treated on an equal footing.Comment: Accepted in Physical Review Letters. Auxiliary and related material can be found at: http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/articles.htm