FAO GAUL: Global Administrative Unit Layers 2015, Country Boundaries (FAO/GAUL/2015/level0)

The Global Administrative Unit Layers (GAUL) compiles and disseminates the
best available information on administrative units for all the countries in
the world, providing a contribution to the standardization of the spatial
dataset representing administrative units. The GAUL always maintains global
layers with a unified coding system at country, first (e.g. departments),
and second administrative levels (e.g. districts). Where data is available,
it provides layers on a country by country basis down to third, fourth, and
lowers levels. The overall methodology consists in a) collecting the best
available data from most reliable sources, b) establishing validation
periods of the geographic features (when possible), c) adding selected data
to the global layer based on the last country boundaries map provided by
the UN Cartographic Unit (UNCS), d) generating codes using GAUL Coding
System, and e) distribute data to the users
(see Technical Aspects of the GAUL Distribution Set).
Note that some administrative units are multipolygon features.