We find that shelf prices are generally lower when there is a coupon available ,and this result
holds as we add a number of fixed effects to control for unobserved changes in demand and costs.
Next we evaluate the patterns of coupons across brands cities and time to gather some suggestive
evidence on a number of possible explanations for the negative relationship between coupons and
shelf prices.We find support for models of price discrimination in oligopoly settings that suggest
inter brand competition can cause all prices to be lower than the uniform(nondiscriminatory)price
(Corts,1 998). We also find evidence suggesting that coupons are used most intensively at the
end of manufacturers' fiscal years,which differ across manufactures.This suggests that brand
managers have incentives to use coupons and price cuts simultaneously to for example,meet
market share targets.We find less support for theories suggesting that the vertical relationship
between manufacturers and retailers affects the correlation between shelf prices and coupons