A Tale of Two Matrix Factorizations

In statistical practice, rectangular tables of numeric data are commonplace, and are often analyzed using dimension-reduction methods like the singular value decomposition and its close cousin, principal component analysis (PCA). This analysis produces score and loading matrices representing the rows and the columns of the original table and these matrices may be used for both prediction purposes and to gain structural understanding of the data. In some tables, the data entries are necessarily nonnegative (apart, perhaps, from some small random noise), and so the matrix factors meant to represent them should arguably also contain only nonnegative elements. This thinking, and the desire for parsimony, underlies such techniques as rotating factors in a search for “simple structure.” These attempts to transform score or loading matrices of mixed sign into nonnegative, parsimonious forms are, however, indirect and at best imperfect. The recent development of nonnegative matrix factorization, or NMF, is an attractive alternative. Rather than attempt to transform a loading or score matrix of mixed signs into one with only nonnegative elements, it directly seeks matrix factors containing only nonnegative elements. The resulting factorization often leads to substantial improvements in interpretability of the factors. We illustrate this potential by synthetic examples and a real dataset. The question of exactly when NMF is effective is not fully resolved, but some indicators of its domain of success are given. It is pointed out that the NMF factors can be used in much the same way as those coming from PCA for such tasks as ordination, clustering, and prediction. Supplementary materials for this article are available online.     

A meta-analytic framework to adjust for bias in external control studies

While randomized controlled trials (RCTs) are the gold standard for estimating treatment effects in medical research, there is increasing use of and interest in using real-world data for drug development. One such use case is the construction of external control arms for evaluation of efficacy in single-arm trials, particularly in cases where randomization is either infeasible or unethical. However, it is well known that treated patients in non-randomized studies may not be comparable to control patients—on either measured or unmeasured variables—and that the underlying population differences between the two groups may result in biased treatment effect estimates as well as increased variability in estimation. To address these challenges for analyses of time-to-event outcomes, we developed a meta-analytic framework that uses historical reference studies to adjust a log hazard ratio estimate in a new external control study for its additional bias and variability. The set of historical studies is formed by constructing external control arms for historical RCTs, and a meta-analysis compares the trial controls to the external control arms. Importantly, a prospective external control study can be performed independently of the meta-analysis using standard causal inference techniques for observational data. We illustrate our approach with a simulation study and an empirical example based on reference studies for advanced non-small cell lung cancer. In our empirical analysis, external control patients had lower survival than trial controls (hazard ratio: 0.907), but our methodology is able to correct for this bias. An implementation of our approach is available in the R package ecmeta .     

Behavioural problems of adolescents in secure residential youth care: Gender differences and risk factors

Adolescents in secure residential care mostly suffer from serious behavioural problems, often accompanied by trauma and adverse family circumstances. This paper presents findings of a comparison of behavioural problems and risk factors of 255 boys and girls (aged 12 to 18 years) in secure residential care in the Netherlands and their association with behavioural problems. A cross-sectional design and standardized questionnaires were used to measure behavioural problems and individual and familial risk factors. By using independent-sample t tests, the severity of these factors in boys and girls was compared, and by using structural equation modelling (SEM), associations between these factors and behavioural problems were investigated. The findings of the study show that post-traumatic stress disorder (PTSD) symptoms, maladaptive emotion regulation, impaired perceived competence and internalizing behavioural problems were more severe in girls than in boys. Boys experienced more severe externalizing behavioural problems and more family problems than girls. Maladaptive emotion regulation, PTSD symptoms, perceived competence and parenting problems were related to behavioural problems. The results indicate that treatment for girls should address PTSD symptoms, perceived competence and maladaptive emotion regulation and that extra attention for family problems in the treatment of boys is warranted.     

Electronic Markets for Truckload Transportation

A wide variety of electronic marketplace formats are used in the Truckload (TL) transportation industry, including combinatorial auctions, private and public exchanges, and electronic catalogs. Combinatorial multi‐attribute auctions are commonly used strategically to populate electronic catalogs, commonly called “routing guides,” with pricing, assignments, and priority logic. Private and public exchanges are used to complement the electronic catalogs in cases where the catalog fails. This paper discusses the TL transportation market, places the procurement of services in the context of electronic marketplace formats, and illustrates how these are currently used.     

Intra-company transfers: The government/corporate interface in the United Kingdom

This paper explores the role of intra-company transfers in the United Kingdom government's labour immigration policy over the last quarter century. It demonstrates their role in determining the number of non-European Economic Area foreigners working in the country and examines the way policy, both generally and specifically, has developed. It presents new statistical data and uses that evidence to examine the interplay between the government and multinational corporations in the determination of a significant element of foreign labour immigration. Its findings demonstrate that intra-company transfers have consistently played a major role in the management of UK labour immigration with a small number of occupations and countries of origin characterizing the system at various times. It concludes that the system has operated through a symbiotic relationship between government and major companies to the mutual benefit of both. However, ‘Brexit’ and the COVID-19 pandemic are leading to reassessment of political and corporate objectives.     

Recent Developments in Greek Industrial Relations: Statutory and Attitudinal Changes Towards Participation and Cooperation

ABSTRACT: Industrial relations in Greece were characterised in the past by labour-management mistrust and conflict, as well as by strong government intervention which invariably influenced the state of industrial relations. Political instability and other serious interruptions, such as World War II, the enemy occupation, civil war and two military dictatorships, made any effort for improvement very difficult, if not impossible, in the 1936-1974 period. Some concerted efforts were made later and especially in the 1980s (with EEC influence and support), which met with considerable success. A series of parliamentary acts and ministerial decrees, restored trade union freedoms, introduced statutory consultation and participation, strengthened collective bargaining, and established an independent agency for the settlement of disputes. Some degree of unity was also achieved among the major political factions represented in the trade union movement. More importantly (and in spite of their traditional reluctance to cooperate) the social partners represented on the employers‘ side by the Association of Greek Industries (SEV), and on the workers‘ side by the Greek General Confederation of Labour (GSEE) are beginning to move towards the development of innovatory systems of cooperation for the solution of problems of mutual concern. Furthermore, there are also some significant structural developments, including the establishment of a growing number of enterprise-level trade unions, which are engaged in contract negotiations and agreements, and participation at the enterprise level. Additionally, appropriate research and training on both sides are helping to meet the socio-economic challenges of the current decade and beyond.