Alistair McKillop of Renfield Recruitment, a one-office firm in central Glasgow dealing with only white-collar staff, reckons there are 70 direct competitors in the local Yellow Pages.

ECONOMIST: Regulation

But White retaliates by returning fire and dropping a yellow paint grenade that makes a direct hit.

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Although he cannot definitely rule out a direct effect by the pollution on the birds' metabolism of the yellow pigment, or its incorporation into their feathers, the correlation between a shortage of caterpillars and faded plumage is strong evidence of a link between pollution, diet and bird colour.

ECONOMIST: Great tits