Bond traders are eyeing a return to a type of trade that left them battered earlier this year - betting on yield curves returning to a more normal shape as slowing economies force central banks to cut interest rates. The shape of the yield curve has been in the spotlight over the last week, with U.S. and European 10-year bond yields rising sharply compared to their shorter-dated peers. Many investors say the big rush into such wagers will come when central banks look poised to cut interest rates to bolster growth.