Estimation of the seemingly unrelated regression model when the error covariance matrix is singular

A two-step generalized least-squares (GLS) estimator proposed by Zellner for seemingly unrelated regression (SUR) models is implementable when the estimated covariance matrix of the errors in the SUR system is non-singular. Violating the premise of non-singularity is a common problem among many applications in economics, business and management. We present methods of resolving this problem and propose an efficient procedure. The simulation study shows that the estimator of Haff performs better for small-sized observations, whereas the estimator of Ullah and Racine performs better for larger sized observations. Furthermore, the Ullah-Racine estimate is simple to calculate and easy to use. The empirical analysis involves the study of the diffusion processes of videocassette recorders across different geographic regions in the US, which exhibits a singular covariance matrix. The empirical results show that the procedures efficiently deal with the problem and provide plausible estimation results.     

Board governance of Strategic Change: An assessment of the literature and avenues for future research

Boards of directors play a central role in governing corporate strategic change. We systematically review corporate governance research on strategic change published over the past 40 years, differentiating between strategic change types and board characteristics. We identify three developments: a focus on specific strategic change types, board composition and structure, and North American listed firms as a dominant study context. Yet, our analysis of the literature shows that research on board governance of interrelated strategic changes, on different board roles and behaviour, and on the governance of strategic changes across different contexts remains underdeveloped. To address these research gaps, we suggest three future research avenues: (1) examining how boards govern interrelated changes in a strategic change portfolio and its evolution over time; (2) studying the mediating relationship between board governance (particularly different board roles and behaviour), strategic changes, and corresponding outcomes; and (3) gaining a better understanding of the role of context in board governance of interrelated strategic changes. We contribute to corporate governance research by developing a framework that synthesizes extant research on the relationships between different board governance variables and strategic change types, highlights important research gaps, and outlines several future research directions to address these gaps. Our framework and literature overview serve as analytical tools to examine whether boards are well-designed and prepared to govern multiple and interrelated strategic changes.