London School of Economics and Political Science

About: London School of Economics and Political Science is a education organization based out in London, United Kingdom. It is known for research contribution in the topics: Population & Politics. The organization has 8759 authors who have published 35017 publications receiving 1436302 citations.

Sparsistency and Rates of Convergence in Large Covariance Matrix Estimation

Abstract: This paper studies the sparsistency and rates of convergence for estimating sparse covariance and precision matrices based on penalized likelihood with nonconvex penalty functions. Here, sparsistency refers to the property that all parameters that are zero are actually estimated as zero with probability tending to one. Depending on the case of applications, sparsity priori may occur on the covariance matrix, its inverse or its Cholesky decomposition. We study these three sparsity exploration problems under a unified framework with a general penalty function. We show that the rates of convergence for these problems under the Frobenius norm are of order (s(n) log p(n)/n)(1/2), where s(n) is the number of nonzero elements, p(n) is the size of the covariance matrix and n is the sample size. This explicitly spells out the contribution of high-dimensionality is merely of a logarithmic factor. The conditions on the rate with which the tuning parameter λ(n) goes to 0 have been made explicit and compared under different penalties. As a result, for the L(1)-penalty, to guarantee the sparsistency and optimal rate of convergence, the number of nonzero elements should be small: sn'=O(pn) at most, among O(pn2) parameters, for estimating sparse covariance or correlation matrix, sparse precision or inverse correlation matrix or sparse Cholesky factor, where sn' is the number of the nonzero elements on the off-diagonal entries. On the other hand, using the SCAD or hard-thresholding penalty functions, there is no such a restriction.

Research and development, spillovers, innovation systems, and the genesis of regional growth in Europe

Abstract: Rodriguez-Pose A. and Crescenzi R. Research and development, spillovers, innovation systems, and the genesis of regional growth in Europe. Regional Studies. Research on the impact of innovation on regional economic performance in Europe has fundamentally followed three approaches: (1) the analysis of the link between investment in research and development (RD (2) the study of the existence and efficiency of regional innovation systems; and (3) the examination of the geographical diffusion of regional knowledge spillovers. These complementary approaches have, however, rarely been combined. Important operational and methodological barriers have thwarted any potential cross-fertilization. This paper tries to fill this gap in the literature by combining in one model R&D, spillovers, and innovation systems approaches. A multiple regression analysis is conducted for all regions of the group of 25 European Union countries (EU-25), including measures of R&D investment, proxies for...

Social Exclusion in Britain 1991—1995

Abstract: The purpose of this paper is to offer a working definition of social exclusion and to operationalize it in such a way that an initial empirical analysis of social exclusion in Britain today can be undertaken. After a brief review of conceptions of social exclusion and some of the key controversies, we operationalize one definition based on the notion of participation in five types of activity—consumption, savings, production, political and social. Using the British Household Panel Survey, indicators for participation on these dimensions are developed and analysed both cross-sectionally and longitudinally for the period 1991–5. We find strong associations between an individual’s participation (or lack of it) on the five different dimensions, and on each dimension over time. However, there is no distinct group of socially excluded individuals: few are excluded on all dimensions in any one year and even fewer experience multiple exclusion for the whole period. The results support the view that treating different dimensions of exclusion separately is preferable to thinking about social exclusion in terms of one homogeneous group.

'High-performance' Management Practices, Working Hours and Work-Life Balance

Abstract: The effects of selected high-performance practices and working hours on work-life balance are analysed with data from national surveys of British employees in 1992 and 2000. Alongside long hours, which are a constant source of negative job-to-home spillover, certain 'high-performance' practices have become more strongly related to negative spillover during this period. Surprisingly, dual-earner couples are not especially liable to spillover - if anything, less so than single-earner couples. Additionally, the presence of young children has become less important over time. Overall, the results suggest a conflict between high-performance practices and work-life balance policies.

Contracts as Reference Points

Abstract: We argue that a contract provides a reference point for a trading relationship: more precisely, for parties' feelings of entitlement. A party's ex post performance depends on whether he gets what he is entitled to relative to outcomes permitted by the contract. A party who is shortchanged shades on performance. A flexible contract allows parties to adjust their outcomes to uncertainty but causes inefficient shading. Our analysis provides a basis for long-term contracts in the absence of noncontractible investments and elucidates why "employment" contracts, which fix wages in advance and allow the employer to choose the task, can be optimal.