The central bank in Taiwan banned Deutsche Bank from trading foreign exchange derivatives for two years in a fight against speculators. The Frankfurt financial institution is prohibited from trading deliverable and non-deliverable futures transactions in Taiwan dollars, the central bank said. Due to global demand for technology products from Taiwan, the Taiwanese dollar has risen against the US dollar to its highest level in more than 23 years. According to the central bank, a case in which foreign banks helped firms specializing in grain trading to engage in currency speculation with futures transactions caused displeasure. This could affect the stability of the Taiwanese foreign exchange market. Letters of punitive action also allegedly went to Citigroup, ING and ANZ for their involvement in the speculative business.