But in the case of goods that change in quality every year, it is much harder to split an increase in nominal ouput or spending between a change in volume and a change in price.

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Computers then measure how a change in a vehicle's price, incentives or features will affect sales volume, where it's losing ground to competitors and, ultimately, profits.

FORBES: How computers tell Ford when to put on a rebate.

Since volume in the service department is low on Wednesdays, it'll offer a half-price oil change if you bring the car in then.

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