Asymmetric price transmission (sometimes abbreviated as APT and informally called 'rockets and feathers' ) refers to pricing phenomenon occurring when downstream prices react in a different manner to upstream price changes, depending on the characteristics of upstream prices or changes in those prices. Asymmetric price transmission (sometimes abbreviated as APT and informally called 'rockets and feathers' ) refers to pricing phenomenon occurring when downstream prices react in a different manner to upstream price changes, depending on the characteristics of upstream prices or changes in those prices.