But the Osaka Stock Exchange positions that were publicly known since OSE publishes weekly data, reflected only half the transactions carried out by Leeson. If he was long the OSE, then it had to be short with twice the number of contracts on SIMEX. Why?For Leeson's official strategy was to take advantage of temporary price differences between Nikkei contracts on SIMEX and OSE ones.This arbitration, which Barings called switching (replacement) Leeson supposed to be bought cheaper contract and to sell simultaneously the most expensive, changing the meaning of the transaction when the price difference would be reduced or would have disappeared. This type of arbitrage has low market risk because positions are always closed.