Websites and embedded third-party elements track all user activities. The users themselves however receive little or no information about this. They also have no insight into the actual use of the collected data and how the data is processed. This missing awareness of the processing possibilities for personal data leads to an information imbalance between users and online service providers. The objectives of this dissertation focus on this imbalance and are divided into three categories: From an economic point of view, this thesis aims at determining a monetary value for the online behaviour of a user; from a social point of view, the thesis monitors recordings of online behaviour, so that users are able to uncover the companies which are collecting data about them; finally, from a technical point of view, a method was developed for estimating how accurately service providers are able to recognize patterns in user behaviour and predict individual online activities.
A software framework was developed for enabling users to collect and visualize their own online activities. The framework automatically expands the collected data with publicly available information about service providers. Thus, services can be clustered based on their owners and their geographic location and their market share can be estimated. The analysis of the collected data revealed that about 80% of the most visited websites contain elements provided by third parties. However, only few third party providers were provided elements to more than 10% of the websites. The accuracy measurement of the analysis capabilities of third party providers revealed that it is possible for them to generate general activity profiles of individual users with only low error rates. However, the precise prediction of concrete future online activities is limited, due to incomplete tracking of user activities. In addition to the influence of the data collection on the prediction, it was found that the distribution of elements in websites also correlates with the advertising revenue of service providers. Thus the most frequently involved third-party providers have the largest market share in digital advertising, which is dominated by American companies. These companies generate most of their revenue in economically strong countries. From the collected data can also be deducted that the value of a person's online behaviour and online ad spending in a country can be linked to the average disposable income and consumption per capita in a country.