"The new guidelines are aimed at further tightening the oversight of the bond-issuance market and specifically cracking down on speculation and arbitrage between some investors and underwriters, " said Yang Weixue, a senior fixed-income analyst at Lianxun Securities.

WSJ: China Tightens Rules on Bond Issuance

Or if you want to go a bit further, why and how there is arbitrage and speculation in financial markets.

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Or, as should be engraved in stone above all trading desks: arbitrage is arbitrage and speculation is speculation and never the twain shall meet.

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But my best guess is that someone on that risk free arbitrage desk moved from risk free pure arbitrage into very definitely not risk free time arbitrage, or speculation as we should call it, then the market moved against his bet.

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This is now time arbitrage or, as I say, speculation.

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