It depends on the length of your ruler - seriously. If you take a little 6 inch ruler and go around every little bayou in Louisiana, you can wind up with a really long coastline.   If you're using GIS, you can figure that any given source is consistent in terms of feature extraction.   The other consideration would be choice of projection.  If you were really ambitious you could reproject each province/territory/estado but I'm not that ambitious. Possible data sources:https://geodata.grid.unep.ch/ - The raw data is in lat/lon so yes choice of projection is important.  The boundary data dates to 1998.GADM (gadm.org) - I want to say this one is lat/lon also.I've got an old copy of "ESRI Data and Maps" also. Joseph McCollumComputer ScientistForest Inventory and AnalysisKnoxville, TN