Labor Productivity: Developments Since 1995

[Excerpt] The paper also explores the reasons for the productivity acceleration and concludes that it likely stemmed from developments in the information technology (IT) sector, including faster technological change in the production of IT goods and the boom in business investment in those goods. Although widely accepted, that explanation raises two questions: Why did productivity growth accelerate further during a period—the years since the 2001 business-cycle peak—when IT investment fell substantially? And why did European economies fail to experience a similar productivity surge even though they had access to the same IT goods that were available in the United States? The paper outlines several possible answers to those questions but concludes that further research will be necessary before economists can provide a consensus answer

A separation of the reactions in photosynthesis by means of intermittent light

Experiments on photosynthesis in intermittent light have been made on two occasions. Brown and Escombe, in 1905, made use of a rotating sector to study the effect of light intensity on the photosynthesis of leaves. They found three-quarters of the light from a given source could be cut out in each revolution of the sector without decreasing the rate of photosynthesis. Willstätter (1918, p. 240) explains that this was probably due to the low concentration of carbon dioxide available for the leaves. The short periods of light would be sufficient to reduce all the carbon dioxide which could reach the cells by diffusion during the dark periods. In 1919-20 Warburg made experiments on Chlorella similar to those of Brown and Escombe on leaves. Instead of stating his results as amount of photosynthesis per total elapsed time, as Brown and Escombe did, he gave photosynthesis per total time during which the cells were illuminated. Since he used sectors which cut out half the incident light in each revolution, the time during which the cells were illuminated was always half of the elapsed time of an experiment. Working with a high intensity of light and a high concentration of carbon dioxide, Warburg found that a given amount of light reduced more carbon dioxide when allowed to fall on the cells intermittently than when allowed to fall on them continuously. The improvement in the yield of the intermittent over the yield in continuous light depended on the frequency of the flashing. With a frequency of four periods per minute the improvement was 10 per cent, and with a frequency of 8000 per minute it was 100 per cent. Warburg proposed two alternative explanations for the improvement in the yield of the intermittent light. Either the reduction of carbon dioxide continues in the dark, or it proceeds twice as fast during the brief light flash as during the same length of time in continuous light. He considers the latter explanation more likely, and assumes that certain steps in the photosynthetic process continue in the dark until a dark equilibrium is reached. After the dark period a short flash of light would find a higher concentration of reactive substance ready for it than is available in continuous light, and would be able to effect more decomposition than an equal amount of continuous light. The experiments described in this paper indicate, we think, that the steps in photosynthesis which proceed in the dark involve what has hitherto been known as the Blackman reaction. Probably the reduction of carbon dioxide is not completed during the photochemical part of the process. A more correct way of representing the sequence of events in intermittent light would be as follows. Two steps are involved in the reduction of carbon dioxide: a reaction in which light is absorbed, followed by a reaction not requiring light -- the so called Blackman reaction. If the light intensity is high the photochemical reaction is capable of proceeding at great speed, but in continuous light it can go no faster than the Blackman reaction. We suppose that the product formed in the photochemical reaction is converted to some other substance by the Blackman reaction, and at the same time the chlorophyll is set free to take part again in the photochemical reaction. If a green cell is illuminated, we think that the photochemical reaction proceeds rapidly until an equilibrium concentration of its product is formed. After this the photochemical reaction proceeds only as fast as the Blackmail reaction removes the intermediate product. If the cell is now darkened, the photochemical reaction stops at once, but the Blackman reaction continues until its raw material, the product formed by the photochemical reaction, is exhausted. After this nothing further happens until the cell is again illuminated. Higher efficiency of the light would be obtained if each light flash lasted only long enough to build up the equilibrium concentration of the intermediate product, and each dark period were long enough to allow the Blackman reaction time to use up all the intermediate product present at the moment the light period ended. In Warburg's flicker experiments the light and dark periods were always of equal length. He found that the amount of work done by the light could be increased by shortening both the light and the dark periods. This indicates that his light periods were too long for maximum efficiency. In the latter part of each light period the photochemical reaction must have been brought down to near the speed of the Blackman reaction. Using 133 light flashes per second, Warburg obtained an improvement of 100 per cent over the continuous light yield. We were able to improve the continuous light yield 300 per cent to 400 per cent by using only 50 flashes per second and making the light flashes much shorter than the dark periods. This opened the possibility of determining the length of the dark period necessary for the complete removal of the intermediate product formed in a light flash of given intensity and duration. Lengthening the dark period should improve the yield until there is time enough for all the intermediate product formed in each light flash to be removed before the next light flash. In this paper we describe experiments which show that the necessary dark time is about 0.03 to 0.4 of a second, depending on the temperature. Further experiments are described to show certain characteristics of the reactions taking place both in the light and in the dark

The challenges of estimating potential output in real time

Potential output is an estimate of the level of gross domestic product attainable when the economy is operating at a high rate of resource use. A summary measure of the economy's productive capacity, potential output plays an important role in the Congressional Budget Office (CBO)'s economic forecast and projection. The author briefly describes the method the CBO uses to estimate and project potential output, outlines some of the advantages and disadvantages of that approach, and describes some of the challenges associated with estimating and projecting potential output. Chief among these is the difficulty of estimating the underlying trends in economic data series that are volatile, subject to structural change, and frequently revised. Those challenges are illustrated using examples based on recent experience with labor force growth, the Phillips curve, and labor productivity growth.Economic development ; Economic conditions

JohnnyVon: Self-Replicating Automata in Continuous Two-Dimensional Space

JohnnyVon is an implementation of self-replicating automata in continuous two-dimensional space. Two types of particles drift about in a virtual liquid. The particles are automata with discrete internal states but continuous external relationships. Their internal states are governed by finite state machines but their external relationships are governed by a simulated physics that includes brownian motion, viscosity, and spring-like attractive and repulsive forces. The particles can be assembled into patterns that can encode arbitrary strings of bits. We demonstrate that, if an arbitrary “seed” pattern is put in a “soup” of separate individual particles, the pattern will replicate by assembling the individual particles into copies of itself. We also show that, given sufficient time, a soup of separate individual particles will eventually spontaneously form self-replicating patterns. We discuss the implications of JohnnyVon for research in nanotechnology, theoretical biology, and artificial life

Stock options as incentive contracts and dividend policy

Executive Stock Option Programs (SOPs) have become the dominant compensation instrument for top-management in recent years. The incentive effects of an SOP both with respect to corporate investment and financing decisions critically depend on the design of the SOP. A specific problem in designing SOPs concerns dividend protection. Usually, SOPs are not dividend protected, i.e. any dividend payout decreases the value of a manager’s options. Empirical evidence shows that this results in a significant decrease in the level of corporate dividends and, at the same time, into an increase in share repurchases. Yet, few suggestions have been made on how to account for dividends in SOPs. This paper applies arguments from principal-agent-theory and from the theory of finance to analyze different forms of dividend protection, and to address the relevance of dividend protection in SOPs. Finally, the paper relates the theoretical analysis to empirical work on the link between share repurchases and SOPs

Non-Perturbative Instabilities as a Solution of the Cosmological Moduli Problem

It is widely accepted that moduli in the mass range 10eV - $10^4$GeV which start to oscillate with an amplitude of the order of the Planck scale either jeopardize successful predictions of nucleosynthesis or overclose the Universe. It is shown that the moduli problem can be relaxed by making use of parametric resonance. A new non-perturbative decay channel for moduli oscillations is discussed. This channel becomes effective when the oscillating field results in a net negative mass term for the decay products. This scenario allows for the decay of the moduli much before nucleosynthesis and, therefore, leads to a complete solution of the cosmological moduli problem.Comment: 8 pages, no figure

Self-Replicating Machines in Continuous Space with Virtual Physics

JohnnyVon is an implementation of self-replicating machines in continuous two-dimensional space. Two types of particles drift about in a virtual liquid. The particles are automata with discrete internal states but continuous external relationships. Their internal states are governed by finite state machines but their external relationships are governed by a simulated physics that includes Brownian motion, viscosity, and spring-like attractive and repulsive forces. The particles can be assembled into patterns that can encode arbitrary strings of bits. We demonstrate that, if an arbitrary "seed" pattern is put in a "soup" of separate individual particles, the pattern will replicate by assembling the individual particles into copies of itself. We also show that, given sufficient time, a soup of separate individual particles will eventually spontaneously form self-replicating patterns. We discuss the implications of JohnnyVon for research in nanotechnology, theoretical biology, and artificial life