This study deals with unplanned terminology development in the subject field of economics within media discourse. It examines how economic terms in Turkish newspapers emerge, are used, and cease. This developmental process is also analyzed through productivity of economic terms and the factors affect them. The subject terms are also analyzed as a whole to show the changes regarding the percentages of language origins. Through diachronic analyses of individual terms, the stages they go through in time are observed. A comprehensive diachronic corpus of 12-year period (1997-2008) was collected from two Turkish newspapers. Subject economic terms were extracted from the corpus. They were tagged for their stem, derivatives, inflected forms, part of speech, length, language origin, and conformity with the Turkish writing system. Productivity was operationalized through the counts of derivatives, inflected forms, co-occurring words, and collocations. Statistical procedures were conducted. Descriptive statistics of the stems showed that only 30 percent of them were of Turkish origin and the rest were of European (French, English, and Italian) and Middle-Eastern (Arabic and Persian). Although the percentage of English stems was not too high (7 percent), the diachronic analysis showed that among the foreign stems, only the ones of English origin showed an upward trend. Turkish origin stems were also rising in the language, whereas other foreign origin terms decreased. Findings suggest that both length and language origin were significant factors in predicting derivational productivity. Stems that are shorter and of Turkish origin tended to generate more derivatives. Similarly derivatives that are of Turkish origin tended to generate more inflected forms than the European origin derivatives. By contrast, length of a derivative was not a factor for inflectional productivity. However, due to the insufficient number of cases, it was not possible to assess the factor of conformity with the writing rules adequately. Diachronic study of individual terms showed that newspaper writers frequently gave definitions for loan terms and attempted to use their own coinages to replace them. The exact locations of the changes and activities in time were pinpointed with the help of the diachronic corpus. The findings support the idea that for efficient terminology planning and maximum derivability, new coinages should be short and neologized by the native resources of the language. In addition, an unbroken diachronic corpus seemed to be necessary in observing terminology development. Future terminology research may benefit from the findings and methodology presented in this study by implementing them to other agglutinative languages and subject fields. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]