An Extension of Ausubel's Auction for Heterogeneous Discrete Goods

Ausubel's dynamic private-values auction for heterogeneous discrete goods, Ausubel (2006), yields an efficient equilibrium outcome but it is designed for a limited class of environments. If bidders' values for bundles of goods are not integers, then the auction mechanism may not yield an efficient allocation without any information on bidders' values. In this paper, I extend Ausubel's auction for heterogeneous discrete goods to real-valued quasilinear utility functions. The mechanism I propose reaches a Walrasian equilibrium price vector in finite "steps" without any additional information on bidders' values. In the extension of Ausubel's auction, truthful bidding constitutes an efficient equilibrium.Auctions, Ausubel auction, heterogeneous goods, discrete goods, price adjustment, tatonnement.

Spatial Impact of New Housing Trends in the Periphery of Istanbul Metropolitan Area

Globalization had a significant effect on socio-economic and spatial changes in Istanbul as the largest city of Turkey following the trends in other cities of the world since the beginning of 1980. In this transformation process which the city center was dislocated and the land rapidly opened for new demands, while the construction sector flowed to business spaces like office blocks, department stores, and five-star hotels; construction companies that prospered ventured to major housing projects in the urban periphery. Therefore, high-income group left the city center due to low quality of life in inner-city areas caused by the drawbacks of rapid urbanization such as intensive residential areas, lack of open and green sites, traffic and parking problems, increasing crime rates. These high-income group housing areas which are brought a new sight as “gated communities”, mostly developed towards the north where the natural resources e.g. forest and water basin of Istanbul Metropolitan Area are located and became a new issue while squatter settlements are still concerned. However, they are planned as individual projects with their own security systems and modern comfortable components; they developed without integration to the metropolitan master plan. The aim of the paper is to examine locational preferences and planning process of high-income group housing projects and prove their effects on the transformation of urban periphery. Their effects on the land values and the role of the central and local governments on this process are examined. Furthermore, this paper attempts to make a contribution to the literature on gated communities by taking account of their spatial impacts. The main findings of paper put forward that existing high-income group housing projects became attraction points for new projects and affected on land use and transportation pattern, while becoming new threats for natural resources of metropolitan periphery.

User-Friendly Locations of Error Messages in Web Forms: An Eye Tracking Study

Error messages presented to users are one of the most important elements of Web forms. Error messages are embedded in different parts of the forms available on the Internet and presented in various formats. One of the measures of a user-friendly error message design is the ability to easily capture users’ attention and facilitate fast error correction. In this empirical study, I tested four different locations of error messages frequently used in Web forms on 32 participants. In addition, I analysed the participants’ interactions with error messages through their eye movements. The results of the study showed that the participants spotted the error message fastest when it was displayed on the right side of the erroneous input field. When error messages displayed further the input field users have less saccades to and fixations on error messages compared to those located near to this field, suggesting that less effort has been spent to understand the given message. However, group mean dif-ferences were not statistically significant for form completion time, error recognition time, the number of saccades, and error correction time