(Bloomberg) -- Tucked away in hours of congressional testimony by Federal Reserve Chair Jerome Powell last month was an admission that the central bank was blindsided by the impact of shrinking its balance sheet four years ago.Most Read from BloombergYellen Says US-China Ties on ‘Surer Footing’ After Beijing VisitJack Ma’s Clash With Beijing Costs Ant, Alibaba $850 BillionChina’s Flood of Plastic, Yellen Departs: Sunday Asia BriefingWall Street Soothsayers Are Bewildered About What’s NextKremlin