This study examines how US discretionary practices developed in the past decade have affected antidumping duty rates against exporters. Using the most recent data on dumping margin calculations, we find that the US Department of Commerce (DOC) has developed discretionary practices in a more nuanced manner to inflate dumping margins, which have primarily targeted market economy exporters. Our case studies document that practices known as targeted dumping and particular market situations appear to serve as trade protectionism for market economy exporters, especially those who could otherwise have received a negative determination without such practices. Furthermore, the DOC has brought an apparent change in its application of discretionary practices after the Trade Extension Preferences Act of 2015, leading to much higher dumping margins for the market economy. Along with empirical and case analyses, we further examine the World Trade Organization (WTO) jurisprudence concerning the extent to which the discretion of an investigating authority in anti-dumping proceedings can be condoned in the WTO.