Over the past five years, the Japanese yen has lost 30% of its value against the US dollar and nearly as much against the pound. The move sent the Japanese yen up 3.5% against the US dollar, a significant rise in foreign-exchange terms that reversed months of depreciation. The Japanese yen stabilised at around 157 to the dollar this week, stronger than the 163 level prior to the intervention. The administration of a short, sharp shock to speculators betting against the Japanese yen might cause them to re-evaluate the trade. Despite its slide, the Japanese yen is probably still overvalued.