The present study has been accepted as a doctoral thesis by the Depart- ment of Economics of the Johann Wolfgang Goethe-University in Frankfurt am Main. It grew out from my five year long participation in two research projects, "Econometric analysis of transaction intensity and volatility on fi- nancial markets," and "Microstructure on financial markets," that were both conducted by the chair of Statistics and Econometrics (Empirical Economic Research) at the Department of Economics and Business Administration, Jo- hann Wolfgang Goethe-University in Frankfurt am Main and financed by the state...