This Masters thesis elaborates on the influence of tax unit on the amount of the personal income tax burden in OECD countries. Its aim is to analyse the effect of the nominal tax rate on the development of the tax units application. In the first part I deal with the possible theoretical settings of the tax unit and assesses the advantages and disadvantages that such settings bring about. The second part reflects the practical way of taxation in relation to a particular taxing unit and the related tax relief taking into consideration the social status of the taxpayer. In the final part, which analyses the current trend in the application of the tax unit in OECD countries, maps the trend developments throughout the history and points out how this trend was influenced by the nominal tax rate, I examine the transition from joint taxation to the individual taxation that had been recorded in OECD countries in recent fifty years and had been predominantly caused by the negative impact of the marginal tax rates on the work incentives of second earners in the household.

Today, with various technology and business standards, organizations face rapid changes in both internal and external environments. To be able to rapidly respond to such changing environments, integration of software systems has entered among the top priorities of many organizations. However, despite extended use of software integration, methods for estimating the business value of implementing such integration are still missing. Besides presenting a conceptual model to define the benefits of systems integration and related causal relationships, this study proposes a method for measuring such benefits in monetary terms. In particular, we  demonstrate how a mathematical programming technique called Data Envelopment Analysis (DEA) can be used to evaluate the business value of software integration. Our method is illustrated using data from 12 organizations. The results indicate significant productivity gains by integrating software systems, which represent the value of software integration in organizations.