Since the 1990s, China has a ‘foreign film quota.’ In the early years, this meant that just a small quote of foreign films were allowed to be imported into China, and in 2012, this was increased to 34 foreign movies per year. The amount of revenue that foreign producers can take from these movies is restricted to 25% (Latham 2007, 185; Ma 2017, 193).
Although Hollywood lobbyists have been negotiating with Chinese film authorities to allow more foreign films to be imported under revenue-sharing terms, there’s been little progress for now – the ongoing looming trade-war has not benefited the situation.
Besides the longstanding cap on foreign films, China also has unofficial ‘Hollywood black-out periods’ in which Hollywood blockbusters are prevented to enter the market so as to boost sales of local productions, a phenomenon dubbed “Domestic Film Protection Month” (国产电影保护月).
"we don't ban films, we just ban all of them except for the ones we let through"
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That's a good thing, not enough places have a good domestic media apparatus. All the good ones were killed by the CIA and NATO during the cold war.