South-South Irregular Migration: The Impacts of China’s Informal Gold Rush in Ghana

This article examines irregular South‐South migration from China to Ghana, and the role it played in transforming livelihoods and broader developmental landscapes. It looks at the entry of approximately 50,000 Chinese migrants into the informal small‐scale gold mining sector from 2008‐2013. These migrants mainly hailed from Shanglin County in Guangxi Province. In Ghana, they formed mutually beneficial relationships with local miners, both legal and illegal, introducing machinery that substantially increased gold production. However, the legal status of Chinese miners was particularly problematic as, by law, small‐scale mining is restricted to Ghanaian citizens. In mid‐2013, President Mahama established a military task force against illegal mining, resulting in the deportation of many Chinese miners. The article examines the experiences of both Chinese migrants and Ghanaian miners. Findings are that irregular migration into an informal sector had long‐lasting impacts and played a significant role in the transformation of economic, political, and physical landscapes in Ghana

On the well-posedness of the rational covariance extension problem

Abstract. In this paper, we give a new proof of the solution of the rational covariance extension problem, an interpolation problem with historical roots in potential theory, and with recent application in speech synthesis, spectral estimation, stochastic systems theory, and systems identification. The heart of this problem is to parameterize, in useful systems theoretical terms, all rational, (strictly) positive real functions havinga specified window of Laurent coefficients and a bounded degree. In the early 1980’s, Georgiou used degree theory to show, for any fixed “Laurent window”, that to each Schur polynomial there exists, in an intuitive systems-theoretic manner, a solution of the rational covariance extension problem. He also conjectured that this solution would be unique, so that the space of Schur polynomials would parameterize the solution set in a very useful form. In a recent paper, this problem was solved as a corollary to a theorem concerning the global geometry of rational, positive real functions. This corollary also asserts that the solutions are analytic functions of the Schur polynomials. After giving an historical motivation and a survey of the rational covariance extension problem, we give a proof that the rational covariance extension problem is well-posed in the sense of Hadamard, i.e a proof of existence, uniqueness and continuity of solutions with respect to the problem data. While analytic dependence on the problem data is stronger than continuity, this proof is much more streamlined and also applies to a broader class of nonlinear problems. The paper concludes with a discussion of open problems. 1