So perhaps there's something we can do coming out of this trip - the mayor and I - to have more exchanges with people from the Shanghai area, because I believe it's very important.

BBC: News | Monitoring | President Clinton on Shanghai radio phone-in

For example, securities exchanges benefit from the network effect because as they attract more traders they become better able to handle additional trading volume.

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It will, to an extent, take over that role from the Conservative Research Department, which has come to concentrate much more on the routine exchanges of political hostilities.

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Find out more about VS Ramachandran's work on Exchanges at the Frontier from the BBC World Service in association with the Wellcome Collection.

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What is clear from these exchanges is that the task Justice Scalia sets for the court is far more challenging than he seems to believe.

ECONOMIST: The politics of justice

More subtly, global exchanges disagree about the value they put on everything from food companies to banks, even after taking account of differences in a firm's local prospects.

ECONOMIST: Stock exchanges

Advisors typically collect higher fees for trading strategies, brokers collect more commissions, exchanges earn a fee from each transaction, and market makers gorge themselves on the bid-ask spread.

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The exchanges have agreed to break trades on nearly 300 stocks that traded more than 60% away from their last price during the volatile 20 minutes that caused most of the damage Thursday.

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