| 1. |
- Casazza, Gabriele, et al.
(author)
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Reproductive biology of the threatened Lilium pomponium (Liliaceae), a species endemic to Maritime and Ligurian Alps
- 2018
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In: Journal of plant research. - : SPRINGER JAPAN KK. - 0918-9440 .- 1618-0860. ; 131:4, s. 633-640
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Journal article (peer-reviewed)abstract
- Pollination ecology and breeding system of Lilium pomponium L. were studied, and their effect on the reproductive outcome was assessed. This species has high conservation interest in Europe, because it is included in Annex V of the EU Habitat Directive and it is one out of the five Lilium species listed in IUCN Global Red List. To achieve our aim, the pollen vectors as well as the effect of bagging, emasculation and artificial pollination on reproductive output were studied. The most frequent visitor was the Lepidopteran Gonepteryx rhamnii. In general, reproductive outputs were close to zero for all the self-pollination treatments; however, geitonogamy and facilitated selfing seem slightly more efficient than autogamy, as also confirmed by self-compatibility and autofertility indices. Altogether, our results suggest a self-incompatible outcrossing breeding system, with a poor capacity for selfing. Nevertheless, climate change and anthropic threats might promote a shift toward self-fertilization, even maladaptive, favouring the few individuals able to produce selfed seeds.
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| 2. |
- Giordani, Paolo
(author)
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An alternative explanation of the price puzzle
- 2004
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In: Journal of Monetary Economics. - : Elsevier. - 0304-3932. ; 51:6, s. 1271-1296
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Journal article (other academic/artistic)abstract
- This paper proposes an explanation for the frequent appearance of a price puzzle in VARs designed for monetary policy analysis. It assumes that the data are generated by a model in which output and output gap are not equivalent, while an econometrician follows the common practice of including only output in the VAR. The omission of the output gap is shown to spuriously produce a price puzzle (and several other incorrect conclusions) in a class of commonly used models. This can happen even if the model admits a triangular identification and if the forecasts produced by the misspecified VAR are optimal. When the model is tested on US data, all predictions are supported. A commodity price index is not needed to solve the puzzle.
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| 3. |
- Giordani, Paolo, et al.
(author)
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Constitutions and central-bank independence : an objection to McCallum's second fallacy
- 2001
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Other publication (other academic/artistic)abstract
- Most of the literature on monetary policy delegation assumes that the government can credibly commit to the delegation contract or that renegotiation involves a cost. This paper provides some foundations for the assumption that renegotiating a delegation contract can be costly by illustrating how political institutions call generate inertia in recontracting, reduce the gains from it or prevent it altogether. Once the nature of renegotiation costs has been clarified, it is easier to see why certain institutions can nlitigate or solve dynamic inconsistencies better than others. The paper points to institutions which give Western democracies the technology to make credible delegation commitments, and argues that the ECB is an example of credible delegation.
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| 4. |
- Giordani, Paolo
(author)
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Essays in monetary economics and applied econometrics
- 2001
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Doctoral thesis (other academic/artistic)abstract
- This dissertation collects five independent essays. The first essay is An Alternative Explanation of the Price Puzzle. The most widely accepted explanation of the price puzzle points to an inadequate performance of the VAR in forecasting inflation. This essay suggests that the finding of a price puzzle is due to a seemingly innocent misspecification in taking the theoretical model to the data: a measure of output gap is not included in the VAR (output alone being used instead), while this variable is a crucial element in every equation of the theoretical models. When the VAR is correctly specified, the price puzzle disappears. Building on results contained in the first paper, the second-- Stronger Evidence of Long-Run Neutrality: A comment on Bernanke and Mihov---improves the empirical performance of standard models on the prediction that a monetary policy shock should have temporary effects on output. It turns out that the same misspecification causing the price puzzle is also responsible for overestimation of the time needed for the effects on output of a monetary policy shock to die out. The point can be proven in a theoretical economy, and is confirmed on US data. Monetary Policy Without Monetary Aggregates: Some (Surprising) Evidence , joint with Giovanni Favara) is the third essay. It points to what seems to be a falsified prediction of models in the New-Keynesian framework. In this framework monetary aggregates are reserved a pretty boring role, so boring that they can be safely excluded from the final lay out of the model. These models predict that a money demand shock should have no effect on output, inflation and interest rate. However, the prediction seems to be quite wrong Inflation Forecast Targeting, joint with Paul Söderlind, takes a step outside the representative-agent framework. In RE models, all agents typically have the same information set, and therefore make the same predictions. However, in the real even professional forecasters show substantial disagreement. This disagreement can have an impact on asset prices and transaction volumes, among other things. However, there is no unique way of aggregating forecasts (or forecast probability density functions) into a measure of disagreement. The paper deals with this problem, surveying some proposed methods. The most appropriate measure of disagreement turns out to depend on the intended use, that is, on the model. Moreover, forecasters underestimate uncertainty. Constitutions and Central-Bank Independence: An Objection to McCallum's Second Fallacy, joint with Giancarlo Spagnolo , is an excursion into the field of Political Economy. The essay provides some foundations for the assumption that renegotiating a delegation contract can be costly by illustrating how political institutions can generate inertia in re-contracting, reduce the gains from it or prevent it altogether. Once the nature of renegotiation costs has been clarified, it is easier to see why certain institutions can mitigate or solve dynamic inconsistencies better than others.
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| 5. |
- Giordani, Paolo, et al.
(author)
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Forecasting macroeconomic time series with locally adaptive signal extraction
- 2010
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In: International Journal of Forecasting. - : Elsevier BV. - 0169-2070 .- 1872-8200. ; 26:2, s. 312-325
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Journal article (peer-reviewed)abstract
- We introduce a non-Gaussian dynamic mixture model for macroeconomic forecasting. The locally adaptive signal extraction and regression (LASER) model is designed to capture relatively persistent AR processes (signal) which are contaminated by high frequency noise. The distributions of the innovations in both noise and signal are modeled robustly using mixtures of normals. The mean of the process and the variances of the signal and noise are allowed to shift either suddenly or gradually at unknown locations and unknown numbers of times. The model is then capable of capturing movements in the mean and conditional variance of a series, as well as in the signal-to-noise ratio. Four versions of the model are estimated by Bayesian methods and used to forecast a total of nine quarterly macroeconomic series from the US, Sweden and Australia. We observe that allowing for infrequent and large parameter shifts while imposing normal and homoskedastic errors often leads to erratic forecasts, but that the model typically forecasts well if it is made more robust by allowing for non-normal errors and time varying variances. Our main finding is that, for the nine series we analyze, specifications with infrequent and large shifts in error variances outperform both fixed parameter specifications and smooth, continuous shifts when it comes to interval coverage.
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| 6. |
- Giordani, Paolo, et al.
(author)
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Inflation forecast uncertainty
- 2003
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In: European Economic Review. - 0014-2921. ; 47:6, s. 1037-1059
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Journal article (other academic/artistic)abstract
- We study the inflation uncertainty reported by individual forecasters in the Survey of Professional Forecasters 1969-2001. Three popular measures of uncertainty built from survey data are analyzed in the context of models for forecasting and asset pricing, and improved estimation methods are suggested. Popular time series models are evaluated for their ability to reproduce survey measures of uncertainty. The results show that disagreement is a better proxy of inflation uncertainty than what previous literature has indicated, and that forecasters underestimate inflation uncertainty. We obtain similar results for output growth uncertainty. (C) 2002 Elsevier B.V. All rights reserved.
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| 7. |
- Giordani, Paolo, et al.
(author)
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Monetary policy without monetary aggregates : some (surprising) evidence
- 2001
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Other publication (other academic/artistic)abstract
- Recent monetary business cycle models with sticky prices assign no role to monetary aggregates, in the sense that the level of output, price and interest rate can be determined without knowledge of the quantity of money. This paper evaluates the empirical validity of this position by studying the effects of money demand shocks for these variables. We use an identified VAR analysis, isolating money-demand shocks by means of identifying restrictions supported by all models in this class. Contrary to the prediction of the theory, real money balances have substantial predictive power for future movements in inflation and output.
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| 8. |
- Giordani, Paolo
(author)
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Stronger evidence of long-run neutrality : a comment on Bernanke and Mihov
- 2001
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Other publication (other academic/artistic)abstract
- Few propositions in macroeconomics are less controversial than long-run money neutrality, yet clear and robust empirical support has not been found in time series studies. Bernanke and Mihov (1998) are comparatively successful in this hunt, but their output response to monetary policy shocks remains stubbornly persistent. This paper argues that the omission of a measure of output gap from the VAR estimated by Bernanke and Mihov lies at the heart of this "excessive" persistence. In the theoretical framework of a New Keynesian model similar to that of Svensson (1997) and Clarida, Gali and Gertler (1999), I prove that this omission induces persistence overestimation under relatively mild assumptions. The inclusion of a proxy for the output gap in the VAR is then shown to drastically increase the evidence for long-run money neutrality on US data, as predicted by the theoretical analysis.
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| 9. |
- Giordani, Paolo, et al.
(author)
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Taking the Twists into Account: Predicting Firm Bankruptcy Risk with Splines of Financial Ratios
- 2014
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In: Journal of financial and quantitative analysis. - : Cambridge University Press (CUP): HSS Journals. - 0022-1090 .- 1756-6916. ; 49:4, s. 1071-1099
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Journal article (peer-reviewed)abstract
- We demonstrate improvements in predictive power when introducing spline functions to take account of highly nonlinear relationships between firm failure and leverage, earnings, and liquidity in a logistic bankruptcy model. Our results show that modeling excessive nonlinearities yields substantially improved bankruptcy predictions, on the order of 70%-90%, compared with a standard logistic model. The spline model provides several important and surprising insights into nonmonotonic bankruptcy relationships. We find that low-leveraged as well as highly profitable firms are riskier than those given by a standard model, possibly a manifestation of credit rationing and excess cash-flow volatility.
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| 10. |
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| 11. |
- Hudson, Lawrence N, et al.
(author)
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The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
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In: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
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Journal article (peer-reviewed)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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| 12. |
- Hudson, Lawrence N., et al.
(author)
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The PREDICTS database : a global database of how local terrestrial biodiversity responds to human impacts
- 2014
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:24, s. 4701-4735
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Journal article (peer-reviewed)abstract
- Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups - including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems - ). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.
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| 13. |
- Hurtado, Pilar, et al.
(author)
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Contrasting Environmental Drivers Determine Biodiversity Patterns in Epiphytic Lichen Communities along a European Gradient
- 2020
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In: Microorganisms. - : MDPI. - 2076-2607. ; 8:12
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Journal article (peer-reviewed)abstract
- Assessing the ecological impacts of environmental change on biological communities requires knowledge of the factors driving the spatial patterns of the three diversity facets along extensive environmental gradients. We quantified the taxonomic (TD), functional (FD), and phylogenetic diversity (PD) of lichen epiphytic communities in 23 beech forests along Europe to examine their response to environmental variation (climate, habitat quality, spatial predictors) at a continental geographic scale. We selected six traits related to the climatic conditions in forest ecosystems, the water-use strategy and the nutrient uptake, and we built a phylogenetic tree based on four molecular markers. FD and climate determined TD and PD, with spatial variables also affecting PD. The three diversity facets were primarily shaped by distinct critical predictors, with the temperature diurnal range affecting FD and PD, and precipitation of the wettest month determining TD. Our results emphasize the value of FD for explaining part of TD and PD variation in lichen communities at a broad geographic scale, while highlighting that these diversity facets provide complementary information about the communities' response under changing environmental conditions. Furthermore, traits such as growth form, photobiont type, and reproductive strategy mediated the response of lichen communities to abiotic factors emerging as useful indicators of macroclimatic variations.
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| 14. |
- Strid, Ingvar, et al.
(author)
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Adaptive hybrid Metropolis-Hastings samplers for DSGE models
- 2010
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Other publication (other academic/artistic)abstract
- Bayesian inference for DSGE models is typically carried out by single block random walk Metropolis, involving very high computing costs. This paper combines two features, adaptive independent Metropolis-Hastings and parallelisation, to achieve large computational gains in DSGE model estimation. The history of the draws is used to continuously improve a t-copula proposal distribution, and an adaptive random walk step is inserted at predetermined intervals to escape difficult points. In linear estimation applications to a medium scale (23 parameters) and a large scale (51 parameters) DSGE model, the computing time per independent draw is reduced by 85% and 65-75% respectively. In a stylised nonlinear estimation example (13 parameters) the reduction is 80%. The sampler is also better suited to parallelisation than random walk Metropolis or blocking strategies, so that the effective computational gains, i.e. the reduction in wall-clock time per independent equivalent draw, can potentially be much larger.
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| 15. |
- Villani, Mattias, et al.
(author)
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Regression density estimation using smooth adaptive Gaussian mixtures
- 2009
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In: Journal of Econometrics. - : Elsevier BV. - 0304-4076 .- 1872-6895. ; 153:2, s. 155-173
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Journal article (peer-reviewed)abstract
- We model a regression density flexibly so that at each value of the covariates the density is a mixture of normals with the means, variances and mixture probabilities of the components changing smoothly as a function of the covariates. The model extends the existing models in two important ways. First, the components are allowed to be heteroscedastic regressions as the standard model with homoscedastic regressions can give a poor fit to heterciscedastic data, especially when the number of covariates is large. Furthermore, we typically need fewer components, which makes it easier to interpret the model and speeds up the computation. The second main extension is to introduce a novel variable selection prior into all the components of the model. The variable selection prior acts as a self-adjusting mechanism that prevents overfitting and makes it feasible to fit flexible high-dimensional surfaces. We use Bayesian inference and Markov Chain Monte Carlo methods to estimate the model. Simulated and real examples are used to show that the full generality of our model is required to fit a large class of densities, but also that special cases of the general model are interesting models for economic data.
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