Bootstrapping I(1) data

A functional law is given for an I(1) sample data version of the continuous-path block bootstrap of Paparoditis and Politis (2001a). The results provide an alternative demonstration that continuous-path block bootstrap unit root tests are consistent under the null.     

Knowledge spillovers in US patents: A dynamic patent intensity model with secret common innovation factors

During the past two decades, innovations protected by patents have played a key role in business strategies. This fact enhanced studies of the determinants of patents and the impact of patents on innovation and competitive advantage. Sustaining competitive advantages is as important as creating them. Patents help sustaining competitive advantages by increasing the production cost of competitors, by signaling a better quality of products and by serving as barriers to entry. If patents are rewards for innovation, more R&D should be reflected in more patent applications but this is not the end of the story. There is empirical evidence showing that patents through time are becoming easier to get and more valuable to the firm due to increasing damage awards from infringers. These facts question the constant and static nature of the relationship between R&D and patents. Furthermore, innovation creates important knowledge spillovers due to its imperfect appropriability. Our paper investigates these dynamic effects using US patent data from 1979 to 2000 with alternative model specifications for patent counts. We introduce a general dynamic count panel data model with dynamic observable and unobservable spillovers, which encompasses previous models, is able to control for the endogeneity of R&D and therefore can be consistently estimated by maximum likelihood. Apart from allowing for firm specific fixed and random effects, we introduce a common unobserved component, or secret stock of knowledge, that affects differently the propensity to patent of each firm across sectors due to their different absorptive capacity.     

Inconsistency of the MLE and inference based on weighted LS for LARCH models

This paper considers a class of finite-order autoregressive linear ARCH models. The model captures the leverage effect, allows the volatility to be arbitrarily close to zero and to reach its minimum for non-zero innovations, and is appropriate for long memory modeling when infinite orders are allowed. However, the (quasi-)maximum likelihood estimator is, in general, inconsistent. A self-weighted least-squares estimator is proposed and is shown to be asymptotically normal. A score test for conditional homoscedasticity and diagnostic portmanteau tests are developed. Their performance is illustrated via simulation experiments. It is also investigated whether stock market returns exhibit some of the characteristic features of the linear ARCH model.     

Dominating estimators for minimum-variance portfolios

In this paper, we derive two shrinkage estimators for minimum-variance portfolios that dominate the traditional estimator with respect to the out-of-sample variance of the portfolio return. The presented results hold for any number of assets d≥4$d\ge 4$ and number of observations n≥d+2$n\ge d+2$. The small-sample properties of the shrinkage estimators as well as their large-sample properties for fixed d$d$ but n→∞$n\to \infty$ and n,d→∞$n,d\to \infty$ but n/d→q≤∞$n/d\to q\le \infty$ are investigated. Furthermore, we present a small-sample test for the question of whether it is better to completely ignore time series information in favor of naive diversification.     

ON THE “PRO‐POORNESS” OF GROWTH IN A MULTIDIMENSIONAL CONTEXT

This paper represents a first attempt to bring together the issues of multidimensional poverty and growth “pro‐poorness” assessments. More specifically, we suggest the use of sequential dominance procedures to test the “pro‐poorness” of observed growth spells when poverty is measured on the basis of income and another discrete well‐being attribute. Sequential procedures are also used to obtain graphical tools that are consistent with the spirit of Ravallion and Chen's growth incidence curve and Son's poverty growth curve. Contrary to traditional unidimensional tests, our method makes it possible to take into account the importance of deprivation correlations at the individual level and thus may reverse results observed with the traditional tools used to check the “pro‐poorness” of growth. An illustration of our approach is given using Turkish data for the period 2003–05.     

Human capital accumulation in R&D-based growth models

This paper develops a model that reproduces the essential aspects of the recent ICT-based economy using the framework of endogenous growth theory in which a central role is played by human capital accumulation. In particular, it considers a multi-sectoral growth model in discrete time with infinite horizon, endogenous growth, embodied technological progress, horizontal differentiation and “lab-equipment” specification of R&D, and with human capital accumulation (represented by the fact that households devote a fraction of their time to schooling), in order to take into account the crucial role of the latter when new technologies are present. In this model it is possible to obtain some important results, both analytically and through simulations, either in the case of constant productivity of schooling and in the case in which this productivity is a function of technological progress. The first conclusion is that the productivity of schooling affects the long run growth of the economy, contrary to the productivities of the other sectors, hence in this model human capital accumulation is the true engine of growth. It is then possible to study the reaction of the economy to different types of shocks, and to compare the results with the empirical evidence. The conclusion is that the model is able to reproduce such evidence, suggesting that the interaction between ICT and human capital is one of the drivers of the recent economic performance.     

Explosive U.S. budget deficit

In this study, we present new evidence that the postwar U.S. federal budget deficit was explosive in nature. Because of the government's inevitable attempts to reduce high or rapidly growing budget deficits, the deficit may contain a substantial component that periodically collapses, which renders the standard unit root tests biased toward stationarity. We apply a newly proposed recursive unit root test for explosiveness, which is known to be powerful to the periodically collapsing component. Although the evidence for explosiveness we found herein is not overwhelming, this study should at the very least serve as a warning against a blind application of standard unit root tests to budget deficits, which may harbor components that periodically collapse.     

Transition probabilities in a problem of stochastic process switching

Extant solutions for state-contingent process switching use first-passage time densities or differential equations. We alternatively employ transition probabilities. These conditional likelihood functions also have obvious appeal for econometric analyses as well as derivative pricing and decision making under absorption and extinction.     

An experimental investigation of wage taxation and unemployment in closed and open economies

We investigate experimentally the economic effects of wage taxation to finance unemployment benefits for a closed economy and an international economy. The main findings are the following. (i) There is clear evidence of a vicious circle in the dynamic interaction between the wage tax and unemployment. (ii) Employment is boosted by budget deficits but subsequent tax rate adjustments to balance the budget lead to employment levels substantially lower than theoretically predicted. (iii) A sales risk for producers due to price uncertainty on output markets appears to cause a downward pressure on factor employment. For labor the wage tax exacerbates this adverse effect.     

基于S3C2410的轮式移动机器人操作系统平台的构建

文章介绍了基于S3C2410微处理器在轮式移动机器人中的一个实际应用,介绍了Windows CE操作系统内核的剪裁和文件系统的改造,对S3C2410的加载过程以及实时检测界面应用程序的开发过程,并进行实验验证了方案的可行性。