Mark Graham recently tallied up the nationality of people who make edits to Wikipedia. He found, for example, that 85 percent of edits to articles about America are made by Americans. Conversely, only 9 percent of edits about Kenya are made by Kenyans. His advice:
Some parts of the world are represented on one of the world's most-used websites predominantly by local people, while others are almost exclusively created by foreigners, something to bear in mind next time you read a Wikipedia article.
Graham's map is below. Via Zoe Pollock.