This research examines whether mandatory price reporting (MPR) impacted price relationships among U.S. hog markets. Markets are cointegrated before and after MPR enactment, but not fully integrated in either period. Terminal markets adjust to shocks in the Iowa-Southern Minnesota market more quickly and Iowa-Southern Minnesota prices adjust to shocks in terminal markets more slowly following MPR enactment. Granger causality tests indicate a causal flow from terminal markets to Iowa-Southern Minnesota prices before MPR and a causal reversal after MPR enactment. These results likely reflect decreases in volume of negotiated sales, particularly in terminal markets, and greater reliance on mandatorily reported prices for market information.