that's pretty ridiculous conspiracy theory! here's more knowledgeable answer: http://www.cnbc.com/id/37019184 http://www.cnbc.com/id/37019184 As near as I ca

that's pretty ridiculous conspiracy theory! here's more knowledgeable answer: http://www.cnbc.com/id/37019184 http://www.cnbc.com/id/37019184 As near as I can tell from talking to market participants, there is no rule on this. This appears to be a compromise reached among the electronic markets. But why 60 percent? Why not, say, 40 percent, or 30 percent? Not clear, but one obvious answer is that there are a lot fewer trades that need to be busted when it's at 60 percent versus say, 40 percent. This saves a lot of grief.