In today's liberalising markets, regulators have yet to figure out the best way to achieve that reserve margin without damaging the new incentives they are trying to introduce.

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However, these branches deliver just 9% of Lloyds' profit - largely because what's being sold is in effect a low-margin mortgage bank, without the benefit of all the other higher margin loans and products that Lloyds also sells its millions of customers.

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Amazon has grown rapidly, though it increasingly looks like a low-margin retailer without the stores, as YCharts pointed out earlier this year.

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