The MiDi is a collection of individual (i.e. firm-to-firm or private individuals-to-firms) investment relations originally collected to calculate aggregate measures of German foreign direct investment (FDI). It is based on an annual data collection on foreign direct investment stocks that was established by the Deutsche Bundesbank in 1976 in accordance with the German Foreign Trade and Payments Regulation ("Aussenwirtschaftsverordnung"), with the intention to get a better and more accurate picture of the structure and scope of inward and outward FDI of German enterprises. Since 1996, individual companies can be traced over time, which made it possible to prepare a micro-level panel dataset for research purposes. Due to changes in data protection regulation, the available anonymized research data covers all years from 1999 until the respective last currently processed year.

Inward and outward foreign direct investment stock relations that German companies are involved in, that are considered as relevant for FDI aggregate statistics, as regulated by the decree "German Foreign Trade and Payments Regulation" ("Aussenwirtschaftsverordnung").

Complete inventory of all units of analysis within the study universe, i.e. "Grundgesamtheit".