Global gold-back exchange-traded funds (ETFs) and similar products recorded $3.9-billion of net inflows across all regions in September, increasing their collective gold holdings by 75.2 t to 2 808 t, the highest levels of all time, the World Gold Council (WGC) said on Tuesday. Holdings surpassed late 2012 levels, at which time the gold price was near $1 700/oz, about 18% higher than current levels, the council said.