[UBS: CME Margin Hike Triggers Retail Influx, Trading Volume of World's Largest Silver ETF Surges] UBS stated that the world's largest silver ETF—iShares Silver Trust (SLV)—is one of the main factors driving the growth in ETF trading volume. Over the past four days, SLV's trading volume hit a new yearly high on three occasions. The Chicago Mercantile Exchange (CME) raised margin requirements, triggering excessive participation from retail investors in SLV. A significant outflow of funds was observed on Monday, while fund flows stabilized on Tuesday.