Signs of financial imbalances are emerging in corporate bond markets, Janet Yellen, the vice-chair of the Federal Reserve, on Wednesday warned.

Though she said there were no "obvious signs" of "significant" financial excess, Yellen told an audience in Tokyo that some areas, such as non-financial corporate bonds, warranted ongoing attention. "Credit spreads on non-financial corporate bonds have dropped sharply since the start of the financial crisis," the vice-chair said. Though the decline