Since the late 1990s deregulation has begun to effect public housing. Some public housing owners sold their whole companies. How do approaches, communication and strategies for collaboration of key actors develop under conditions of structural change? The focus of the comparative empirical case studies in Kiel, Osnabrück and Wilhelmshaven rests with a governance approach on the fields of urban development and the housing market. An evaluation allows conclusions to be drawn for praxis and further research. EXECUTIVE SUMMARY Certainly since the late 1990s, if not earlier, deregulation as well as local authority debt reduction eventually has gegun to take effect on local authority housing. In this context, the owners of public housing sold large quantities of their housing stock as well as whole housing companies. Characteristic for the current situation is a tension between a stable stock of rented property (both in condition and market value) on the one side and international ‚new investors’, who are largely driv- en by financial interest and acquire large property portfolios on the other side. This tension is specifi- cally grounded in the particularities of housing as economic and social good. While the amortisation of capital investment per housing unit in the rented sector is only realised after decades by means of rental income, the ‚new investors’ are primarily interested in a high and fast capital turnover. The sale of publicly owned housing property, which is often in high need of modernisation and re- furbishment, to international investors creates new opportunities for the housing economy due to different approaches to management and marketing. At the same time, such sale to ‚new investors’ also bears risks for housing markets, urban renewal and urban planning. In this context, local authorities that have sold their entire housing stock not only face a growing range of actors with increasingly diversified economic interests. In addition, local authorities are ex- pected to initiate processes of integrated urban development in order to respond to structural change and its consequences. Complicating matters further, they have to rely exclusively on third party actors to secure the housing provision for low-income households. Research into newly emerging and changing relationships between actors in local housing markets is only in its beginnings in the field of regional studies. Possible consequences of the market entry of ‚new investors’ for urban development, the housing market as well as for local cooperation have so far rarely been studied. It remains unknown until now - whether the market entry of ‚new investors’ has an impact on the strategic orientation for action of local authorities and housing stockholder, and - Whether collective strategic orientations for action are possible between new and old competitors in the housing economy. This study intends to close this research gap. Over its ten chapters, this doctoral thesis pursues as its key question: following the complete sale of local authority housing stock, how do approaches, communication as well as strategies for collaboration of key actors in the housing markets develop under conditions of structural change? The focus of the comparative empirical case studies rests on the fields of urban development and the housing market. The period under investigation were the years from 1999 to 2009. Grounded in a comprehensive analysis of theory and secondary statistical data, the research addresses a predominately application-oriented remit. By means of analysing the cities of Kiel, Osnabrück and Wilhelmshaven, the following aims are pursued and subjected to a systematic comparison: Analysis of the application of local authority instruments to achieve aims of urban development and housing policy, Account of the new demands on local authority remit, approach and negotiating positions as well as approaches to housing following the market entry of ‚new investors’, Account of the consequences of the market entry of ‚new actors’ on urban development, the hous- ing market and for safeguarding the statuory tasks of local authorities. Key findings of the study are as follows: The consequences of structural change shape the strategic action, both collective and competitive, of local authorities as well as housing actors disproportionately stronger than the market entry of new actors. The income generated from stock sales did not achieve a lasting debt relief for local authorities. No structural changes to local authority budgetary policy took place. With the market entry of ‚new investors’ • no immediate strategic re-orientation of local authority activity or of long-established housing actors in the market actors took place, • locally strongly heterogeneous approaches of new and old housing actors as well as local authorities could be evidenced, • local authorities’ negotiating positions in the housing market and urban development were weakened, despite their differing strategic and collaborative approaches, • the implementation of local authority interests for a sustainable urban development became more difficult in principle, • the purpose (also to a large extent the communication), and thus the responsibility, of private ac tors in processes of urban development and in the housing market was lost, • local authority planning instruments and incentives lost their ability to influence the existing mar ket base due to the generally low interest and willingness of the ‚new investors’ to engage or col laborate in investment.