Strategic interactions of urban land developers in the housing market

This thesis studies the supply side of the housing market taking into account the strategic interactions that occur between urban land developers. The thesis starts by reviewing the literature on new housing supply, concluding that there are very few studies where strategic interactions are taken into account. Next, we develop a model with two urban land developers, who rst decide the quality of housing and then compete in prices, considering that the marginal production costs depend on the housing quality. First, we analyze the price competition game and characterize the Nash equilibrium of the price game. Finally, we examine the rst stage of the game and determine numerically the subgame perfect Nash equilibrium (SPNE) of the quality-price game. In the price competition game, our results show that the equilibrium price of an urban land developer is an increasing function of its own quality, while it is a non-monotonic function of the rival s quality. The behavior of the equilibrium pro ts reveals that, in general, urban land developers gain by di¤erentiating their quality. However, the urban land developer located at the Central Business District (CBD), may prefer to have the same quality than the rival when transportation costs are high by exploiting its locational advantage. The analysis of the rst stage of the game also reveals that, in general, the rms best response is to di¤erentiate their quality and that, in most cases, there are two subgame perfect Nash equilibria that involve quality di¤erentiation. However, the results depend on transportation costs and the quality valuation parameter. For small quality valuations, in equilibrium, the market is not fully covered and, if the unit transportation costs are high, only the urban land developers located at the CBD operates. For higher quality valuations, all the consumers are served. Furthermore, the equilibrium qualities and pro ts are increasing with quality valuation parameter. RESUMO: Esta tese estuda a oferta no mercado da habitação, tendo em conta as interações es- tratégicas que ocorrem entre os produtores de habitação. A tese revê a literatura sobre a oferta de habitação, concluindo que existem poucos estudos que tenham tido em conta as interações estratégicas. De seguida, desenvolvemos um modelo com dois produtores de habitação, que primeiro decidem a qualidade da habitação e depois competem em preços, considerando que os custos marginais de produção dependem da qualidade. Primeiro analisamos o jogo em preços e caracterizamos o equilíbrio de Nash. Posteriormente, ex- aminamos o primeiro estágio do jogo e determinamos numericamente o equilíbrio perfeito em todos os subjogos (SPNE) do jogo. No jogo de competição em preços, os resultados mostram que, o preço de equilíbrio, é uma função crescente da qualidade da habitação, sendo uma função não monótona da qualidade do rival. O lucro de equilíbrio revela que, geralmente, os produtores de habitação têm ganhos em diferenciar a qualidade. No entanto, o produtor localizado no Centro (CBD), pode preferir oferecer a mesma qualidade que o rival, caso os custos unitários de transporte sejam elevados, através da sua vantagem de localização. A análise do primeiro estágio do jogo, revela que, geralmente, a melhor resposta de um produtor é a de diferenciar a qualidade. Na maior parte dos casos existem dois SPNE que envolvem essa diferenciação. No entanto, os resultados dependem dos custos unitários de transporte e da valorização da qualidade por parte do consumidor. Para uma reduzida valorização da qualidade, em equilíbrio, o mercado não é totalmente coberto e, se o custo unitário de transporte é elevado, apenas o produtor localizado no CBD opera no mercado. Para uma valorização elevada da qualidade, todos os consumidores são servidos. Além disso, as qualidades e os lucros de equilíbrio são crescentes com a valorização da qualidade.

Mechanical properties of adobe blocks used in building construction in Huambo Province - Angola

Despite significant advances in building technologies with the use of conventional construction materials (as concrete and steel), which significantly have driven the construction industry, earth construction have demonstrated its importance and relevance, as well as it has matched in an efficient and eco-friendly manner the social housing concerns. The diversity of earth construction techniques allowed this material to adapt to different climatic, cultural and social contexts until the present time. However, in Angola, the construction with earth is still associated with population fringes of weak economic resources, for which, given the impossibility of being able to acquire modern construction materials (steel, cement, brick, among others), they resort to the use of available natural materials. Furthermore, the lack of scientific and technical knowledge justifies the negative appreciation of traditional building techniques, and the derogatory way how are considered the earth constructions in Angolan territory. Given the country's current development status, and taking into account the environmental requirements and the real socio-economic sustainability of Angola, it is considered that one of the viable and adequate options, could be the recovering and upgrading of the ancestral techniques of earth construction. The purpose of this research is to develop the technical and scientific knowledge in order to improve and optimize these construction solutions, responding to the real problems of housing quality as well as to the current social, economic and environmental sustainability requirements. In this paper, a description of the physical and mechanical characteristics of the adobes typically used in the construction of traditional houses in some localities of Huambo, province in Angola, is carried out. The methodology was based on mechanical in-situ testing in adobe blocks manufactured with traditional procedures: i) tensile strength evaluated with the bending test and compressive strength test on earth blocks specimens; and, ii) durability and erodibility test by Geelong method adopting the New Zealand standard (NZS) procedures (4297: 1998; 4297: 1998 and 4297: 1999). The results allow the characterization of the materials used in the construction of raw earth in the Huambo region, contributing to the development of knowledge of these sustainable and traditional housing constructive solutions with a strong presence in Angola [1, 2]. This study is part of a larger project in the area of Earth Construction [3], which aims to produce knowledge which can stimulate the use of environmental friendly construction materials and contribute to develop constructive solutions with improved performance, durability, comfort, safety and sustainability.