Definition: Main source of livelihood
Population censuses - UNECE
The "main source of livelihood" is the principal source from which the consumption of each person was financed during a specified reference period.
It is recommended to give preference to a long reference period, such as the preceding twelve months or the calendar year, in order to take account of sources which may actually provide an income at periodic or seasonal intervals (such as income from seasonal activities, payment of quarterly benefits from pension plans, annual payment of scholarships or dividends, income from intermittent secondary activities, etc.). Income in kind as well as in cash should be taken into account.
United Nations Economic Commission for Europe (UN-ECE) (in cooperation with Eurostat), "Conference of European Statisticians Recommendations for the 2010 Censuses of Population and Housing", New York and Geneva, 2006