The Chinese government does not like speculative bubbles. They are currently issuing warnings about the stock market. They are restricting lending. They are telling people not to sell any property to buy stocks. To the Chinese government, speculative bubbles cause chaos and disorder and may ruin people's lives. That in turn threatens the government's position. We saw how the Chinese government began to warn and freeze bank accounts in 2013 when bitcoin was bubbling.
From the point of view of Chinese exchanges, bubbles are a bad thing. If a bubble develops, the government will come back in and start shutting things down. What if China's top three exchanges made a pact to keep bitcoin from bubbling? They would have nice, calm business for years. This is my conspiracy theory. They can short bitcoin, engaging in stop hunting with phantom coins to take money from heavily leveraged buyers. At the same time, they contain any major rallies so they don't catch heat from their government. At the same time, miners are selling coins everyday anyway, so the default pressure is down.
Only an absolutely enormous bullwhale who keeps buying and withdrawing coins could possibly expose such a plan. And I don't think we have a bullwhale like that.
In what way exactly would they do that? They cant influence every world exchange, so if they are presenting false data, they would have to pay up every cashout difference from their own pocket..
The more viable solution would be to report accounts that are buying large amounts of bitcoins to their govenment, which could then find a way to "legaly" remove such a trader.
In any way, i don't see this theory as plausible.
I have made a suggestion some time back on how they could influence the market by holding on or selling off the fee's from trades, but that is also not enough to stop a true bubble from happening,
even tho even the daily fee's are not negligible, especialy if it is a coordinated action from more exchanges together.
cheers