Balanced sampling of boxes from batches for assessing quality of fruits and vegetables in EU countries

Quality & Quantity - The best evaluation for the proportion of defective units in a batch of fruits and vegetables can be achieved by an exhaustive checking of all the boxes in the batch, that...     

Inference on factor structures in heterogeneous panels

This paper develops an estimation and testing framework for a stationary large panel model with observable regressors and unobservable common factors. We allow for slope heterogeneity and for correlation between the common factors and the regressors. We propose a two stage estimation procedure for the unobservable common factors and their loadings, based on Common Correlated Effects estimator and the Principal Component estimator. We also develop two tests for the null of no factor structure: one for the null that loadings are cross sectionally homogeneous, and one for the null that common factors are homogeneous over time. Our tests are based on using extremes of the estimated loadings and common factors. The test statistics have an asymptotic Gumbel distribution under the null, and have power versus alternatives where only one loading or common factor differs from the others. Monte Carlo evidence shows that the tests have the correct size and good power.     

An application of padé approximation to volatility modeling

This paper studies the dynamic relationship between future volatility and implied and historical volatility using data from Alegría and Rodríguez [1997]. The methodological approach forms part of the theoretical research being carried out in numerical analysis and especially from the rational Padé approximation. This tool helps to characterize simple computational methods in order to study questions about dynamic modelization of doubly infinite series. Considering noncausal series, where the expectations provided by economic theory or empirical evidence are included in available sample data, leads to dynamic specifications suitable not only from the perspective of fitting available data, but also from their predictive performance when compared to traditionally used formulae based merely on data analysis.     

Equilibrium with endogenous technological changes: Theory and applications

In this paper we use a continuous-time general equilibrium model to analyze the problem of evaluating new irreversible investment opportunities that take the form of technological changes. Being a new technology, by definition, not perfectly correlated with the existing ones, the traditional spanning assumption invoked by the Real Option literature is not applicable in this context and a general equilibrium approach provides a more suitable framework. We analyze the problem of optimal consumption and investment of the representative individual in the context of the Cox Ingersoll and Ross (1895) model. We characterize the solution of the model under different assumptions about the utility function of the representative individual and about the parameters describing the technologies in the economy. A major result obtained from the model is the possibility of jumps in the equilibrium rate of return at the time in which technological changes are implemented. This is particularly interesting considering the fact that such jumps are obtained endogenously from the solution of the optimization problem and not imposed by “ad hoc” assumptions on the evolution of some variables.

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Riassunto Un modello di equilibrio economico generale in tempo continuo è utilizzato per analizzare il problema di valutare una nuova, irreversibile, opportunità di investimento che si presenta sotto forma di innovazione tecnologica. Essendo, per definizione, la nuova tecnologia non perfettamente correlata con le tecnologie esistenti, la letteratura delle “opzioni reali” non è applicabile ed un modello di equilibrio economico generale fornisce un ambiente più adatto allo studio del problema. Facendo uso del modello di Cox Ingersoll and Ross (1985) si fornisce una soluzione sotto diverse ipotesi riguardanti la struttura delle preferenze e la natura dell'innovazione tecnologica. Un interessante risultato è la derivazione di possibili discontinuità nel tasso di interesse di equilibrio in corrispondenza dell'adozione della nuova tecnologia.

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I would like to express my gratitude to Vasant Naik, David Peterson, Raman Uppal and especially Burton Hollifield and Tan Wang for helpful discussions and suggestions.     

Bootstrapping Financial Time Series

It is well known that time series of returns are characterized by volatility clustering and excess kurtosis. Therefore, when modelling the dynamic behavior of returns, inference and prediction methods, based on independent and/or Gaussian observations may be inadequate. As bootstrap methods are not, in general, based on any particular assumption on the distribution of the data, they are well suited for the analysis of returns. This paper reviews the application of bootstrap procedures for inference and prediction of financial time series. In relation to inference, bootstrap techniques have been applied to obtain the sample distribution of statistics for testing, for example, autoregressive dynamics in the conditional mean and variance, unit roots in the mean, fractional integration in volatility and the predictive ability of technical trading rules. On the other hand, bootstrap procedures have been used to estimate the distribution of returns which is of interest, for example, for Value at Risk (VaR) models or for prediction purposes. Although the application of bootstrap techniques to the empirical analysis of financial time series is very broad, there are few analytical results on the statistical properties of these techniques when applied to heteroscedastic time series. Furthermore, there are quite a few papers where the bootstrap procedures used are not adequate.     

Funding a PAYG pension system: the case of Italy

Italy is characterised by a mature pay‐as‐you‐go social security system and by particularly adverse population projections. Given these trends, the social security contribution rate is expected to increase above its current high level. This hinders the development of employer‐provided pension funds and introduces a significant wedge between labour cost and earnings that discourages both labour demand and labour supply. Any proposal to reduce payroll taxes and to reform the system in the direction of partial funding has to cope with the state of Italian public finances. Italy has to comply with the Stability and Growth Pact that imposes constraints on budget deficit and debt trends. Using micro data from the Bank of Italy's Survey of Household Income and Wealth and official population projections, we estimate future employment trends under different demographic and macroeconomic scenarios and compute the cost of the transition. We show that it would be substantially reduced if positive effects on employment were induced by the payroll tax reduction.     

Tax Discounting in a High‐debt Economy*

This paper estimates a consumption function for Belgium that allows for government debt discounting and for the overall discounting of the future (reflecting the consumers’ planning horizon or precautionary savings). It also allows for substitutability or complementarity effects from government expenditures. Results suggest that consumers do take into account (future) government activity. Ricardian Equivalence is rejected however, since we cannot reject a relatively short planning horizon or a precautionary savings motive for the consumers. We use bootstrapped distributions for inference since the instrumental variables estimators used may have non‐standard distributions. This procedure also helps to tackle potential endogeneity and sample size problems.     

Sources of crime in the state of Veracruz: The role of female labor force participation and wage inequality

Abstract

In recent years, crime has become a serious concern in Mexico as its increase has detrimentally affected government institutions and economic growth. There is considerable speculation among policy analysts about the causes of the increase in crime. Whereas some analysts attribute the increase to a rise in income inequality, others believe internal migration and a loss of morals are the roots of criminal behavior. This research shows that at least for the Mexican state of Veracruz, wage inequality and labor force participation have an important impact on crime. When gender is considered, however, the impact is more complicated than it seems. An increase in women's labor force participation decreases the overall number of alleged violent offenders. However, the number of alleged rapists and grievous bodily harm offenders increases as women's wage distribution improves. The results shed light on the gender dimensions of the economics of crime.     

A within-trial cost-effectiveness analysis of panitumumab compared with bevacizumab in the first-line treatment of patients with wild-type RAS metastatic colorectal cancer in the US

Abstract

Aims: This analysis investigated the cost-effectiveness of panitumumab plus mFOLFOX6 (oxaliplatin, 5-fluorouracil, and leucovorin) compared with bevacizumab plus mFOLFOX6 in the first-line treatment of patients with wild-type RAS metastatic colorectal cancer (mCRC).

Materials and methods: The cost-effectiveness analysis was developed from a third-party payer perspective in the US and was implemented using a partitioned survival model with health states for first-line treatment (progression-free), disease progression with and without subsequent active treatment, and death. Survival analyses of patients with wild-type RAS mCRC from the PEAK head-to-head clinical trial of panitumumab vs bevacizumab were performed to estimate time in the model health states. Additional data from PEAK informed the amount of each drug consumed, duration of therapy, subsequent therapy use, and toxicities related to mCRC treatment. Literature and US public data sources were used to estimate unit costs associated with treatment and duration of subsequent active therapies. Utility weights were calculated from patient-level data from panitumumab trials in the first-, second-, and third-line settings. A life-time perspective was taken with future costs and outcomes discounted at 3% per annum. Scenario, one-way, and probabilistic sensitivity analyses were performed.

Results: Compared with bevacizumab, the use of panitumumab resulted in an incremental cost of US $60,286, and an incremental quality-adjusted life-year (QALY) of 0.445, translating into a cost per QALY gained of US $135,391 in favor of panitumumab. Results were sensitive to wastage and dose rounding assumptions modeled.

Limitations: Progression-free and overall survival were extrapolated beyond the follow-up of the primary analysis using fitted parametric curves. Costs and quality of life were estimated from multiple and different data sources.

Conclusions: The efficacy of panitumumab in extending progression-free and overall survival and improving quality of life makes it a cost-effective option for first-line treatment of patients with wild-type RAS mCRC compared with bevacizumab.