The chairman of the Swiss National Bank (SNB), Philipp Hildebrand, resigned on Monday with immediate effect, following revelations that his wife Kashya been involved in currency trading. He told a news conference he had "no knowledge" of his wife's transaction, on which she later made a profit. According to an investigation carried out by accountants PricewaterhouseCoopers (PwC) on the bank's orders, Mrs Hildebrand bought $504,000 on 15th August because she wanted to have half of the family's assets in US dollars. In early September, the central bank intervened to try to weaken the strong franc. Four weeks later, when the family converted $516,000 back into Swiss francs, they made a profit on the transaction because the franc had fallen against the dollar in that time. The Swiss National Bank cleared Mr Hildebrand of any wrongdoing in a report which detailed his wife's dealings in late December. This report was published last week amid new allegations that Mr Hildebrand personally authorised foreign exchange dealings using his personal account three weeks before, and three weeks after Switzerland introduced a currency cap.