(Bloomberg) After seven years of preparation, $2 billion in compliance costs and one false start, the biggest shake-up to European regulation in a decade is finally here. With so much at stake, investors are likely to sit on their hands for now.Trading volumes slumped ahead of the changes, according to two brokers with knowledge of the matter, with client business at one major brokerage in Europe almost non-existent as the rules were poised to take effect Wednesday.

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