Arising from the author experience as a practicing CPA, this book is quite different from other research in this field, as it confronts the subject of audit quality from a pragmatic perspective. The first goal of Jonas Tritschler is to develop an audit quality metric on national audit firm level. Financial reporting errors, as detected by the German enforcement institutions during examinations, which subsequently are published in the German Federal Gazette by the involved companies, are the data basis for this measurement. Using the developed audit quality metric, the second goal of this study is to analyze audit quality differences of selected audit firms by comparing their deployed audit input factors such as employee competence (ratio of certified professionals to total audit staff), experience of employees (average tenure of employees in years) and client-specific experience (client fluctuation rate). Results indicate a correlation between audit quality according to the developed metric and the operationalized audit input factors mentioned above.