4.72. As mentioned in connection with the measurement of visitor flows (Chapter III), outbound tourism expenditure can be measured at or near the border as outbound visitors return from their trip or, as in the case of domestic tourism expenditure, through the use of household‑type surveys.
4.73. Under certain conditions, the measurements of a country’s outbound tourism expenditure obtained through a household‑type survey can be used directly or as an input for the measurement of inbound tourism expenditure in the countries visited. When used as such an input, the measurements from the survey are known as mirror statistics (see chapt. III, sect. C.2.2.4).