In PWP-001, Borenstein, Cameron and Gilbert test and confirm the common belief that retail gasoline prices react more quickly to increases in crude oil prices than to decreases. Most of the response to a crude oil price increase shows up in the pump price within 2 weeks, while decreases are passed along more gradually over at least 4 weeks. Among the possible explanations for this asymmetry are market power some producers or distributors, or inventory adjustment costs. By analyzing price transmission at different points in the distribution chain the authors attempt to shed light on these theories. They find that wholesale prices show a significant asymmetry in responding to crude oil price changes, due to the asymmetric adjustment between commodity spot prices for crude oil and generic gasoline, which may reflect inventory adjustment effects. A significant asymmetry also appears in the response of retail prices to wholesale price changes. The authors argue that this probably reflects short run market power among retail gasoline sellers.