So, I really can’t speak to their accuracy, but apparently their network of tracked webpages is quite big, they are measuring unique visitors (not page loads) a

So, I really can’t speak to their accuracy, but apparently their network of tracked webpages is quite big, they are measuring unique visitors (not page loads) and they are doing country level weighing of the data. Whether that makes them more accurate? I really don’t know. But I could very well imagine that for those tracking firms their sample is heavily US and Europe biased (where different browsers as in the rest of the world might dominate), so doing some weighing may increase their accuracy. Or not. I really don’t know. Some light googling does reveal that this is a highly contentious topic with people from all sides screaming at each other about questions of methodology. Do with that info what you will.