(Via @Verfassungklage)
Researchers have examined DNS censorship, e.g. in which countries you get the most manipulated DNS replies, and for what kinds of websites.
Article (in German): http://www.heise.de/newsticker/meldung/Studie-So-heftig-wird-das-Domain-Name-System-manipuliert-3812266.html
Paper (in English): https://www.usenix.org/system/files/conference/usenixsecurity17/sec17-pearce.pdf