The benchmark 10-year Japanese government bond yield hit zero percent Tuesday for the first time on record as tumble in Tokyo shares boosted demand for safe-haven debt, Reuters reported. Traders reckon that it is a matter of time before the 10-year JGB yield falls into the negative with the Bank of Japan having adopted negative interest rates late last month. The Nikkei was down more than 4%, caught up in the risk-averse mood that hit eurozone and US equity markets overnight.