Explainer: How does negative interest rates policy work?

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ISHARES 20+ YEAR TREASURY BOND ETF (NASDAQ: TLT) Delayed: 84.88 --0 (-0%)
Previous Close $84.88    52 Week High $143.62 
Open $84.88    52 Week Low $118.66 
Day High $84.88    P/E N/A 
Day Low $84.88    EPS $0.00 
Volume 117,576