Applying Time Series Decomposition to Construct Index-Tracking Portfolio

This study proposes a new method for creating an index-tracking portfolio using time series decomposition. First, we construct index-tracking portfolios of stocks chosen because their price movements mimic that of the Dow-Jones Industrial Average. Our method utilizes similarities of constituent stocks to the benchmark that are assessed by distances of time series trends derived from decomposing original series. Although the portfolios chosen by our method reasonably tracked the performance of the benchmark, they did not surpass the clustering approach discussed in earlier studies. Therefore, we examined what causes tracking error and found that two causes for deficiencies in our similarity-based method, which are unintended irregular movements of holding stocks and highly correlated relationships within stocks in the portfolio. To overcome them and to improve tracking performance, we propose a similarity-balanced approach that is another index-tracking method with alternate use of similarity. Doing so improved the tracking performance by avoiding the problem of high correlation among the stocks chosen under the initial method.     

Why did farmers stop cultivating NERICA upland rice varieties in central Benin?

New Rice for Africa (NERICA) was developed by the Africa Rice Center by crossing high-yielding Asian rice (Oryza sativa L.) with locally adapted African rice (Oryza glaberrima Steud.). Community-based seed production of NERICA varieties was introduced in a village in central Benin in 2006 through seed dissemination projects. It was reported that high-adoption rates of these varieties were mainly due to high demand by development projects for seed dissemination, and to incentives (i.e. selling the rice seed at a higher than local market price to a local extension service) for farmers to grow NERICA varieties. A follow-up survey was undertaken after the seed dissemination projects ended to examine the change in the cultivation of NERICA varieties. About half of the farmers had ceased cultivation of NERICA varieties in 2011. The reasons for abandonment were the combined effects of reduced seed demand and low yields, which were attributed to a lack of access to credit and training on NERICA cultivation practices. The majority of the farmers did not abandon rice cultivation, but grew other high-yielding varieties, including one aromatic variety for which there was market demand. We conclude that to avoid immediate reductions in the adoption of new varieties after projects are terminated and to enhance agricultural sustainability, the varieties should be introduced in conjunction with appropriate group training on their cultivation, and the project should target farmers who do not have off-farm businesses. Furthermore, access to credit should also be enhanced, and the marketability of the varieties should be assessed.     

CLAIMING SPACE,LAND AND ECOLOGY: Mapping Geographies of Indigenous and Decolonial Urbanisms in Taipei

The city is often understood as the antithesis of Indigeneity. In Taiwan, a settler colony where the Han Chinese have colonized Austronesian Indigenous peoples, dominant understandings and representations situate Indigenous vibrancy outside large cities such as Taipei and Kaohsiung, despite the large-scale urbanization of Indigenous peoples over the past several decades. This essay is based on long-term ethnographic research in Taipei and explores how urbanized Indigenous people in the Taiwanese metropolis persist in claiming the city's space, land and ecology despite both cartographic and physical displacements of their presence. It maps out emerging Indigenous and decolonial urbanisms in Taiwan, discussing the work of Indigenous artists and the spatial and ecological practices of urban Indigenous community residents.