Neutral Rate Research Articles

Pension decrement rates across Europe – Are they too low?

Abstract In light of an ageing population, many European countries are aiming to increase the effective retirement age. Pension decrement rates play a key role in this as they determine the financial incentives for early retirement. In the following, a model is developed to calculate decrement rates which lead to financial neutrality of the decision on when to retire. The model is applied to 19 European countries. Results show that in most countries, official decrement rates tend to be lower than neutral rates. A sensitivity analysis and several alternative model variants underscore that, for the majority of countries, this result seems to be robust to the assumptions taken.

Estimación de la tasa de interés real neutral para Costa Rica

Un banco central que utilice la tasa de interés como instrumento de control monetario requiere contar con una estimación de la tasa de interés real neutral (TIRN) como referencia para tomar las decisiones de política conducentes a lograr su objetivo de inflación. Este documento aborda por primera vez la estimación de la tasa de interés real neutral, utilizando datos de una tasa de política monetaria para Costa Rica, establecida en junio del 2011 por el Banco Central de Costa Rica como su instrumento de control monetario. Considerando información mensual para el período 2009-2015 y combinando las estimaciones provenientes de diversas metodologías, la TIRN para Costa Rica se estima en torno a 1,4%.

Fitness cost of reassortment in human influenza.

Reassortment, which is the exchange of genome sequence between viruses co-infecting a host cell, plays an important role in the evolution of segmented viruses. In the human influenza virus, reassortment happens most frequently between co-existing variants within the same lineage. This process breaks genetic linkage and fitness correlations between viral genome segments, but the resulting net effect on viral fitness has remained unclear. In this paper, we determine rate and average selective effect of reassortment processes in the human influenza lineage A/H3N2. For the surface proteins hemagglutinin and neuraminidase, reassortant variants with a mean distance of at least 3 nucleotides to their parent strains get established at a rate of about 10−2 in units of the neutral point mutation rate. Our inference is based on a new method to map reassortment events from joint genealogies of multiple genome segments, which is tested by extensive simulations. We show that intra-lineage reassortment processes are, on average, under substantial negative selection that increases in strength with increasing sequence distance between the parent strains. The deleterious effects of reassortment manifest themselves in two ways: there are fewer reassortment events than expected from a null model of neutral reassortment, and reassortant strains have fewer descendants than their non-reassortant counterparts. Our results suggest that influenza evolves under ubiquitous epistasis across proteins, which produces fitness barriers against reassortment even between co-circulating strains within one lineage.

Branching Brownian motion and selection in the spatial $\Lambda$-Fleming–Viot process

We ask the question when will natural selection on a gene in a spatially structured population cause a detectable trace in the patterns of genetic variation observed in the contemporary population?. We focus on the situation in which 'neighbourhood size', that is the effective local population density, is small. The genealogy relating individuals in a sample from the population is embedded in a spatial version of the ancestral selection graph and through applying a diffusive scaling to this object we show that whereas in dimensions at least three, selection is barely impeded by the spatial structure, in the most relevant dimension, $d=2$, selection must be stronger (by a factor of $\log(1/\mu)$ where $\mu$ is the neutral mutation rate) if we are to have a chance of detecting it. The case $d=1$ was handled in Etheridge et al. (2015). The mathematical interest is that although the system of branching and coalescing lineages that forms the ancestral selection graph converges to a branching Brownian motion, this reflects a delicate balance of a branching rate that grows to infinity and the instant annullation of almost all branches through coalescence caused by the strong local competition in the population.

Froude-Stanton modeling of heat and mass transfer in large vertical spaces of high-rise buildings

Understanding physics of heat and mass transfer inside large vertical spaces is a major challenge for high-rise fire safety. Due to the size of a high-rise building, experimental studies based on sub-scaled models play an important role in high-rise heat and mass transfer research. Froude modeling method is probably the most common approach for sub-scaling. However, Froude modeling has been found incapable of obtaining accurate temperature predictions from the sub-scaled experiments, especially near building boundaries where there exists significant heat transfer between smoke and the boundaries. In this paper, a new modeling method, Froude-Stanton modeling, is developed for both mechanically-driven and naturally-driven thermal smoke spreads, in which heat transfer is taken into consideration in the energy balance equation. The flow resistance of the internal shaft structure is also considered using a lumped method. To verify the new method, series of experiments were conducted on three shafts with different sizes and material using both Froude and Froude-Stanton methods. The results, including temperature profile, relative neutral plane level and thermal smoke flow rate, are compared between the two modeling methods, and it was found that the new Froude-Stanton modeling method is more accurate.

Effect of lignin linkages with other plant cell wall components on in vitro and in vivo neutral detergent fiber digestibility and rate of digestion of grass forages

The objective of this study was to correlate in vitro and in vivo neutral detergent fiber (NDF) digestibility (NDFD) with the chemical composition of forages and specific chemical linkages, primarily ester- and ether-linked para-coumaric (pCA) and ferulic acids (FA) in forages fed to dairy cattle. The content of acid detergent lignin (ADL) and its relationship with NDF does not fully explain the observed variability in NDFD. The ferulic and p-coumaric acid linkages between ADL and cell wall polysaccharides, rather than the amount of ADL, might be a better predictor of NDFD. Twenty-three forages, including conventional and brown midrib corn silages and grasses at various stages of maturity were incubated in vitro for measurement of 24-h and 96-h NDFD. Undigested and digested residues were analyzed for NDF, acid detergent fiber (ADF), ADL, and Klason lignin (KL); ester- and ether-linked pCA and FA were determined in these fractions. To determine whether in vitro observations of ester- and ether-linked pCA and FA and digestibility were similar to in vivo observations, 3 corn silages selected for digestibility were fed to 6 ruminally fistulated cows for 3 wk in 3 iso-NDF diets. Intact samples and NDF and ADF residues of diet, rumen, and feces were analyzed for ester- and ether-linked pCA and FA. From the in vitro study, the phenolic acid content (total pCA and FA) was highest for corn silages, and overall the content of ester- and ether-linked pCA and FA in both NDF and ADF residues were correlated with NDF digestibility parameters, reflecting the competitive effect of these linkages on digestibility. Also, Klason lignin and ADL were negatively correlated with ether-linked ferulic acid on an NDF basis. Overall, esterified FA and esterified pCA were negatively correlated with all of the measured fiber fractions on both a dry matter and an NDF basis. The lignin content of the plant residues and chemical linkages explained most of the variation in both rate and extent of NDF digestion but not uniformly among forages, ranging from 56 to 99%. The results from the in vivo study were similar to the in vitro data, demonstrating the highest total-tract aNDF digestibility (70%; NDF analysis conducted with α-amylase and sodium sulfite) for cows fed the corn silage with the lowest ester- and ether-linked pCA content in the NDF fraction. In this study, digestibility of forage fiber was influenced by the linkages among lignin and the carbohydrate moieties, which vary by hybrid and species and most likely vary by the agronomic conditions under which the plant was grown.

The effects of foreign shocks when interest rates are at zero

AbstractIn a two‐country DSGE model, the effects of foreign demand shocks on the home country are greatly amplified if the home economy is constrained by the zero lower bound on policy interest rates. This result applies even to countries that are relatively closed to trade such as the United States. Departing from many of the existing closed‐economy models, the duration of the liquidity trap is determined endogenously. Adverse foreign shocks can extend the duration of the trap, implying more contractionary effects for the home country. The home economy is more vulnerable to adverse foreign shocks if the neutral rate is low—consistent with “secular stagnation”—and trade openness is high.

¿Por qué las tasas de interés son tan bajas?+

The low interest rates are a global anomaly that was patented after the outbreak of the so-called “Great Recession”. However, a little more than eight years away from the epiphenomenon of the low cost of capital, this trend does not appear to have changed significantly (despite recent attempts by the United States to reverse this cycle), which means working under new conditions of operation and design of economic policies for the future. The present paper seeks to develop the different explanatory hypotheses that infer the low interest rates both in current dates and in the years to come. Within the main ideas is given particular importance to the hypothesis of secular stagnation, understood as a permanent gap between the neutral interest rate of the economy with the interest rate used by central banks. In the conclusions, some possible lines of research are cited, same that are derived from explaining the low interest rates from the perspective of secular stagnation.

The radiation environment on the surface of Mars - Summary of model calculations and comparison to RAD data

The radiation environment at the Martian surface is, apart from occasional solar energetic particle events, dominated by galactic cosmic radiation, secondary particles produced in their interaction with the Martian atmosphere and albedo particles from the Martian regolith. The highly energetic primary cosmic radiation consists mainly of fully ionized nuclei creating a complex radiation field at the Martian surface. This complex field, its formation and its potential health risk posed to astronauts on future manned missions to Mars can only be fully understood using a combination of measurements and model calculations. In this work the outcome of a workshop held in June 2016 in Boulder, CO, USA is presented: experimental results from the Radiation Assessment Detector of the Mars Science Laboratory are compared to model results from GEANT4, HETC–HEDS, HZETRN, MCNP6, and PHITS. Charged and neutral particle spectra and dose rates measured between 15 November 2015 and 15 January 2016 and model results calculated for this time period are investigated.

Conserved Nonexonic Elements: A Novel Class of Marker for Phylogenomics.

Noncoding markers have a particular appeal as tools for phylogenomic analysis because, at least in vertebrates, they appear less subject to strong variation in GC content among lineages. Thus far, ultraconserved elements (UCEs) and introns have been the most widely used noncoding markers. Here we analyze and study the evolutionary properties of a new type of noncoding marker, conserved nonexonic elements (CNEEs), which consists of noncoding elements that are estimated to evolve slower than the neutral rate across a set of species. Although they often include UCEs, CNEEs are distinct from UCEs because they are not ultraconserved, and, most importantly, the core region alone is analyzed, rather than both the core and its flanking regions. Using a data set of 16 birds plus an alligator outgroup, and 3600–3800 loci per marker type, we found that although CNEEs were less variable than bioinformatically derived UCEs or introns and in some cases exhibited a slower approach to branch resolution as determined by phylogenomic subsampling, the quality of CNEE alignments was superior to those of the other markers, with fewer gaps and missing species. Phylogenetic resolution using coalescent approaches was comparable among the three marker types, with most nodes being fully and congruently resolved. Comparison of phylogenetic results across the three marker types indicated that one branch, the sister group to the passerine falcon clade, was resolved differently and with moderate (70%) bootstrap support between CNEEs and UCEs or introns. Overall, CNEEs appear to be promising as phylogenomic markers, yielding phylogenetic resolution as high as for UCEs and introns but with fewer gaps, less ambiguity in alignments and with patterns of nucleotide substitution more consistent with the assumptions of commonly used methods of phylogenetic analysis.

Weakly dissipative dust acoustic solitons in the presence of superthermal particles

An investigation of the linear and non‐linear properties of low‐frequency electrostatic (dust acoustic) waves in a collisional dusty plasma with negative dust grains, Maxwellian electrons, and κ‐distributed ions is carried out. Low dust–neutral collisions accounting for dissipation (wave damping effect) is considered. The linear properties of dust acoustic excitations are discussed for varying values of relevant plasma parameters. It is shown that large wavelengths (beyond a critical value) are overdamped. In the limit of low dust–neutral collision rate, we have derived a damped Korteweg de Vries (KdV) equation by using the reductive perturbation technique. Supplemented by vanishing boundary conditions, the time‐varying solution of damped KdV equation leads to a weakly dissipative negative potential soliton. The soliton evolution with the damping parameter and other physical plasma parameters (superthermality, dust concentration, ion temperature) is delineated.

MAVEN measured oxygen and hydrogen pickup ions: Probing the Martian exosphere and neutral escape

AbstractSoon after the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft started orbiting Mars, the SEP (Solar Energetic Particle), SWIA (Solar Wind Ion Analyzer), and STATIC (Supra‐Thermal and Thermal Ion Composition) instruments on board the spacecraft detected planetary pickup ions. SEP can measure energetic (>60 keV) oxygen pickup ions, the source of which is the extended hot oxygen exosphere of Mars. Model results show that these pickup ions originate from tens of Martian radii upstream of Mars and are energized by the solar wind motional electric field as they gyrate back toward Mars. SWIA and STATIC can detect both pickup oxygen and pickup hydrogen with energies below ~30 keV and created closer to Mars. In this study, data from the SEP, SWIA, and STATIC instruments containing pickup ion signatures are provided and model‐data comparisons are shown. During the times when MAVEN is outside the Martian bow shock and in the upstream undisturbed solar wind, the solar wind velocity measured by SWIA and the solar wind (or interplanetary) magnetic field measured by the MAG (magnetometer) instrument can be used to model pickup oxygen and hydrogen fluxes. By comparing measured pickup ion fluxes with model results, the Martian thermal hydrogen and hot oxygen neutral densities can be probed outside the bow shock, providing a helpful tool in constraining estimates of neutral oxygen and hydrogen escape rates. Our analysis reveals an order of magnitude density change with Mars season in the hydrogen exosphere, whereas the hot oxygen exosphere was found to remain steadier.

Ultraviolet C ii and Si iii Transit Spectroscopy and Modeling of the Evaporating Atmosphere of GJ436b

Abstract Hydrogen gas evaporating from the atmosphere of the hot-Neptune GJ436b absorbs over 50% of the stellar Lyα emission during transit. Given the planet’s atmospheric composition and energy-limited escape rate, this hydrogen outflow is expected to entrain heavier atoms such as C and O. We searched for C and Si in the escaping atmosphere of GJ436b using far-ultraviolet Hubble Space Telescope COS G130M observations made during the planet’s extended H i transit. These observations show no transit absorption in the C ii 1334,1335 Å and Si iii 1206 Å lines integrated over [−100, 100] km s−1, imposing 95% (2σ) upper limits of 14% (C ii) and 60% (Si iii) depth on the transit of an opaque disk and 22% (C ii) and 49% (Si iii) depth on an extended highly asymmetric transit similar to that of H i Lyα. C+ is likely present in the outflow according to a simulation we carried out using a spherically symmetric photochemical-hydrodynamical model. This simulation predicts an ∼2% transit over the integrated bandpass, consistent with the data. At line center, we predict the C ii transit depth to be as high as 19%. Our model predicts a neutral hydrogen escape rate of g s−1 ( g s−1 for all species) for an upper atmosphere composed of hydrogen and helium.

Brain enlargement and dental reduction were not linked in hominin evolution

The large brain and small postcanine teeth of modern humans are among our most distinctive features, and trends in their evolution are well studied within the hominin clade. Classic accounts hypothesize that larger brains and smaller teeth coevolved because behavioral changes associated with increased brain size allowed a subsequent dental reduction. However, recent studies have found mismatches between trends in brain enlargement and posterior tooth size reduction in some hominin species. We use a multiple-variance Brownian motion approach in association with evolutionary simulations to measure the tempo and mode of the evolution of endocranial and dental size and shape within the hominin clade. We show that hominin postcanine teeth have evolved at a relatively consistent neutral rate, whereas brain size evolved at comparatively more heterogeneous rates that cannot be explained by a neutral model, with rapid pulses in the branches leading to later Homo species. Brain reorganization shows evidence of elevated rates only much later in hominin evolution, suggesting that fast-evolving traits such as the acquisition of a globular shape may be the result of direct or indirect selection for functional or structural traits typical of modern humans.

Crises in Economic Thought, Secular Stagnation, and Future Economic Research

Crises in Economic Thought, Secular Stagnation, and Future Economic Research

Brazil: monetary policy and the neutral interest rate

PurposeThe purpose of this paper is to analyze the conduct of monetary policy in Brazil and estimate the country’s neutral real interest rate.Design/methodology/approachThe authors make use of a state-space macroeconomic model representation.FindingsThe period of analysis goes from 2003 up to the end of 2013 and the results show that the country’s natural rate of interest was around 4.2 percent in December 2013.Originality/valueOne of the main differences of this work is the inclusion of variables such as the real exchange rate and world interest rate. This is important because these variables play an important role in the definition of the interest rate and, consequently, in the definition of the neutral interest rate.

The Neutral Rate and the Summary of Economic Projections

This note uses information provided in the quarterly Summary of Economic Projections (SEP) of FOMC meeting participants to extract estimates of the neutral federal funds rate--defined as the value of the federal funds rate that is "neither expansionary nor contractionary if the economy were operating near its potential"--in the short and longer run.

The Effects of Foreign Shocks When Interest Rates are at Zero

In a two-country DSGE model, the effects of foreign demand shocks on the home country are greatly amplified if the home economy is constrained by the zero lower bound on policy interest rates. This result applies even to countries that are relatively closed to trade such as the United States. Departing from many of the existing closed-economy models, the duration of the liquidity trap is determined endogenously. Adverse foreign shocks can extend the duration of the trap, implying more contractionary effects for the home country. The home economy is more vulnerable to adverse foreign shocks if the neutral rate is low – consistent with "secular stagnation" – and trade openness is high.

Effect of the planet shine on the corona: Application to the Martian hot oxygen

AbstractSystematic observations of the Martian hot oxygen corona by Imaging Ultraviolet Spectrograph on Mars Atmosphere and Volatile and EvolutioN can be used to constrain estimates of the current neutral oxygen escape rate. In this paper, we investigate the effect of the photons emitted from the thermosphere and lower exosphere on the emissivity of the hot oxygen corona at 130.4 nm. We compare this source of illumination, generally neglected, to the direct solar illumination used to convert the O I 130.4 triplet brightness into line‐of‐sight column density. This study is performed using a radiative transfer model with two Maxwellian oxygen populations, assuming spherical symmetry for the cold and hot oxygen densities. Contribution to the corona from the illumination of the exosphere by the sunlit atmosphere depends on the amount of cold oxygen and varies with altitude and solar zenith angle. An analytic formulation to take into account variations of this effect with respect to the hot oxygen kinetic temperature is proposed. The effect of the atmosphere sunlit should be general and occur on other planets for other very optically thick resonance lines.

Lower for Longer: Neutral Rate in the U.S.

We use a semi-structural model to estimate neutral rates in the United States. Our Bayesian estimation incorporates prior information on the output gap and potential output (based on a production function approach) and accounts for unconventional monetary policies using estimates of “shadow” policy rates. Results show a significant trend decline in the neutral real rate post-1990s, driven only in part by a decline in trend growth, whereas other factors (including excess global savings and risk premia) matter. Neutral rates likely turned negative during the global financial crisis and are expected to increase only gradually looking forward.