For the purposes of the GFP ranking, Total Populations are used to as the starting point for all other population-related values including Labor Force, Available Military Manpower and those Fit for Military Service. Generally, the higher the base population, the larger the military fighting force. Based on latest available figures, Total Population data is through 2015.
Sources: CIA.gov, CIA World Factbook, wikipedia.com, public domain print and media sources and user contributions. Some values may be estimated when official sources are lacking.