as the us economic rebound continues to dazzle the mood music in the world’s biggest bond market is getting darker short interest in the 12 billion ishares 20 year treasury bond exchangetraded fund ticker tlt now clocks in at 25 of shares outstanding the highest since early 2017 according to data from ihs markit ltd meanwhile investors are ditching the etf in droves tlt has posted outflows every day so far this week putting the fund on track for weekly withdrawals of over 1 billion  the worst stretch since november bloomberg data show