Although the proposal to write down the face value of privately held Greek-government debt by 50% would be substantial and welcome, Greece's stock of debt would, even on best assumptions, still add up to 120% of GDP by 2020.

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Another objection to Fairtrade is that certification is predicated on political assumptions about the best way to organise labour.

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Every year we try to do an honest, reasonable, conservative forecast to make sure that we are basing our budget assumptions on the best possible forecast that we can.

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Admittedly, these assumptions probably deliver the best-case scenario and conclusions.

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"This is a hope-for-the-best pre-Budget... not a cautious set of assumptions, " said BBC economics editor Evans Davis.

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"There are a lot of complex assumptions necessary to do adjustments, and reasonable people will disagree about the best way to proceed, " she says.

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Because these are tech markets, constantly evolving and complex, most assumptions about the scope of these markets and competitive effects within them are imperfect at best.

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