This research examines whether mandatory price reporting (MPR) impactedprice relationships among U.S. hog markets. Markets are cointegrated beforeand after MPR enactment, but not fully integrated in either period. Terminalmarkets adjust to shocks in the Iowa-Southern Minnesota market more quicklyand Iowa-Southern Minnesota prices adjust to shocks in terminal markets moreslowly following MPR enactment. Granger causality tests indicate a causalflow from terminal markets to Iowa-Southern Minnesota prices before MPR anda causal reversal after MPR enactment. These results likely reflectdecreases in volume of negotiated sales, particularly in terminal markets,and greater reliance on mandatorily reported prices for marketinformation.