UNCTAD compiles FDI statistics based on national international sources. There is an apparent lack of comparability of FDI data reported by different countries. The methodology for compiling these data varies between countries. For a given transaction, host country and home country often do not register it in exactly the same way.
For example, country A may include re-invested earnings in its outflow statistics while country B receiving this FDI may not include the earnings in its inflow statistics. Furthermore, corporate accounting practices and valuation methods differ between countries. These two factors lead to discrepancies in FDI data.