"We will look at whether price variation clauses are appropriate at all, " said an Ofcom spokeswoman.

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The desire is also substantiated by real estate prices for urban residential space, which are 40 to 200 percent higher than in traditional suburban neighborhoods -- this price variation can be found both in cities and small communities equipped with walkable infrastructure, he said.

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Food director of British Retail Consortium, Andrew Opie said that there is "a variation in price between those in the top quarter of dairy production and those who aren't and farmers who are lucky are those in supermarket supply chains".

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As it happens, most of the variation in the price of oil over the past 40 years has reflected changes in the value of the dollar (the denominator) rather than the value of oil (the numerator).

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And while they say there can be significant variations in some of these, it seems one of the reasons Brent crude continues to appeal is that there's least variation in its price, at around one US cent per barrel over a long period.

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Separate factories allow for more variation, but at the price of fewer economies of scale.

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Three professors (from Stanford, INSEAD and MIT, respectively) have come up with a variation on this theme: that the price paid can also influence behaviour.

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The council document said following more detailed investigations a "variation" - or difference between the agreed price list, called the the "schedule of rates" - and the actual amount charged by MITIE was found.

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The house-price measures compiled by the Halifax bank and the Nationwide building society are designed to avoid distortions caused by variation in the type of property being sold.

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