Over the past week, CME has raised margin requirements on precious metals contracts three times in a row, reigniting discussions across the market. Many traders are once again asking whether the exchange is adjusting risk parameters in response to market conditions.This kind of debate is nothing new. Similar arguments have surfaced repeatedly in past episodes whenever sharp moves in silver prices were followed by rapid margin increases.Looking back at the silver market in 2011, the pace of margin requirement adjustments and the price action that followed may offer a more sober reference point for today’s market.Between April and May 2011, silver prices surged rapidly, reaching an all-time high of nearly USD 50 per ounce in late April to early May. The rally was soon followed by a sharp col