Analysis of growth curve data by using cubic smoothing splines

Longitudinal data frequently arises in various fields of applied sciences where individuals are measured according to some ordered variable, e.g. time. A common approach used to model such data is based on the mixed models for repeated measures. This model provides an eminently flexible approach to modeling of a wide range of mean and covariance structures. However, such models are forced into a rigidly defined class of mathematical formulas which may not be well supported by the data within the whole sequence of observations. A possible non-parametric alternative is a cubic smoothing spline, which is highly flexible and has useful smoothing properties. It can be shown that under normality assumption, the solution of the penalized log-likelihood equation is the cubic smoothing spline, and this solution can be further expressed as a solution of the linear mixed model. It is shown here how cubic smoothing splines can be easily used in the analysis of complete and balanced data. Analysis can be greatly simplified by using the unweighted estimator studied in the paper. It is shown that if the covariance structure of random errors belong to certain class of matrices, the unweighted estimator is the solution to the penalized log-likelihood function. This result is new in smoothing spline context and it is not only confined to growth curve settings. The connection to mixed models is used in developing a rough testing of group profiles. Numerical examples are presented to illustrate the techniques proposed.     

The Role of Profit Sharing in Dual Labour Markets with Flexible Outsourcing

We combine profit sharing for high‐skilled workers and outsourcing of low‐skilled tasks in a partly imperfect dual domestic labour market, which means that only low‐skilled labour is represented by a labour union. In that framework we analyse how the implementation of profit sharing for high‐skilled workers influences the amount of outsourcing and the labour market outcome for low‐skilled worker. By doing this, we use some specific assumptions, e.g. exponentially increasing outsourcing costs or the wage for low‐skilled workers will be determined by a union whereas the wage for high‐skilled workers is given. Assuming that low‐skilled labour and outsourcing are interchangeable we show that profit sharing has a positive effect on the wage for low‐skilled workers and helps to decrease wage dispersion. However, under these circumstances, profit sharing enhances outsourcing. Concerning the employment effects for high‐ and low‐skilled workers, we show that there is an employment reducing effect due to higher wages for low‐skilled work, which can be offset by higher productivity of highly skilled workers, as the domestic labour inputs complement each other.     

Inference and rare event simulation for stopped Markov processes via reverse-time sequential Monte Carlo

We present a sequential Monte Carlo algorithm for Markov chain trajectories with proposals constructed in reverse time, which is advantageous when paths are conditioned to end in a rare set. The reverse time proposal distribution is constructed by approximating the ratio of Green’s functions in Nagasawa’s formula. Conditioning arguments can be used to interpret these ratios as low-dimensional conditional sampling distributions of some coordinates of the process given the others. Hence, the difficulty in designing SMC proposals in high dimension is greatly reduced. Empirically, our method outperforms an adaptive multilevel splitting algorithm in three examples: estimating an overflow probability in a queueing model, the probability that a diffusion follows a narrowing corridor, and the initial location of an infection in an epidemic model on a network.     

Lean thinking in the highways construction sector: motivation,implementation and barriers

The interest in lean thinking in the UK’s civil construction industry is on the rise. The research presented in the paper evaluates the adoption of lean thinking in the highways construction sector by investigating 7 motivation factors, 20 lean techniques and 16 barriers through in-depth interviews with 20 sector managers and a questionnaire survey of 110 responses. The findings show the existence of strong external motivational factors for lean thinking such as clients’ push and companies’ expectation of winning more contracts alongside lean’s operational benefits. Limited adoptions of the lean techniques, mostly in the stepwise process improvement cycle, the Last Planner System and Visual Management, were determined. This raises concerns about ‘pseudo-lean’ practices in the sector. Lack of standardisation, insufficient benefit capturing, insufficient know-how, insufficient control of the entire value stream and limited view to the techniques were found as the top barriers.     

Ludic encounters – understanding surveillance through game metaphors

This article explores the connections between game studies and surveillance studies. Although much of previous research analyzes surveillance as an oppressive practice, a more critical approach has recently identified the playful and enjoyable sides of watching and exposing. Surveillance in fact has many playful and game-like functions, which have not yet been addressed in their full extent. In this article, the vocabulary of play and game is used in order to uncover these game-like functions or surveillance practices. Five distinct game metaphors are presented: (1) cat-and-mouse, (2) hide-and-seek, (3) labyrinth, (4) sleight-of-hand and (5) poker. These metaphors reveal connections between enjoyment and control. Their implications are discussed both in urban settings and in virtual surroundings. In this article it is argued that faking, tricking and camouflaging have become persistent elements of urban and virtual cultures. There is no single authority watching, nor single context of surveillance and/or play. Rather, there are multiple players with variable motives. Examining the game elements of surveillance facilitates a broader understanding of how this practice moves beyond power and discipline. It also shows how surveillance and games are more intertwined than might have previously been recognized.     

Does International Outsourcing Really Lower Workers’ Income?

We analyze the impact of international outsourcing on income, if the domestic labor market is imperfect, i.e. there is a bilateral bargaining between a firm and a labor union. In our analysis we distinguish between the cases where the parties negotiate over the wage only and where they negotiate over both wage and profit sharing. We find in the first case that outsourcing has an ambiguous effect on the workers’ income, while it increases the workers’ income in the second case. For the optimal amount of international outsourcing, we find that, depending on the wage effect of outsourcing, in a pure wage bargaining system it can be higher or lower than the level where domestic and foreign marginal labor costs are the same. In contrast, in a wage and profit share bargaining system, the amount of outsourcing lies below this level.