In discussing the estimate of an elasticity, the text mentions changes in the prices of rival brands as a lurking factor. Can you think of another? If the prices in the equation between price and...

In discussing the estimate of an elasticity, the text mentions changes in the prices of rival brands as a lurking factor. Can you think of another?

If the prices in the equation between price and quantity are expressed in a different currency (such as euros at 1.2 per dollar), how does the elasticity change?