(Bloomberg) -- US Bitcoin exchange-traded funds have posted their longest run of daily net outflows since listing at the start of the year, part of a wider retreat from riskier assets in a challenging period for global markets.Most Read from BloombergHow Americans Voted Their Way Into a Housing CrisisWorld's Second Tallest Tower Spurs Debate About Who Needs ItThe Plan for the World’s Most Ambitious Skyscraper RenovationUC Berkeley Gives Transfer Students a Purpose-Built Home on CampusRome May St