While industry inventories the whereabouts of widgets, tourism tracks the transit of real people. In both realms numbers count.
The Technical Subgroup on the Movement of Natural Persons - Mode 4 is a subgroup of the UN Statistical Data (UNSD) section. The UNSD acts as Chair and Secretariat of the Subgroup whose mandate is to build a statistical framework to measure the economic impact of the movement of natural persons, and in particular of Mode 4, on the home and host countries.
The objectives of the work of the Technical Subgroup comprise:
UN Trade in Services
http://unstats.un.org/unsd/tradeserv/default.htm
The Technical Subgroup (TSG) on the Movement of Natural Persons - Mode 4
http://unstats.un.org/unsd/tradeserv/subgroup.htm