The yen has tumbled well past levels touted as red lines for Japan and at a pace that has traders asking when authorities might start buying the currency to support it — and why they haven’t already done so. The currency fell to a 34-year low against the dollar Friday after the Bank of Japan indicated financial conditions will remain easy, with losses accelerating in late trading in New York. A public holiday in Japan on Monday may reduce liquidity in foreign-exchange markets and heighten the risk of further sharp moves in either direction. Policymakers have repeatedly warned that depreciation won’t be tolerated if ... (full story)