One of the biggest fears about Donald Trump’s approach to the economy was that he might try to undermine the Federal Reserve’s independence and press it to cut interest rates. So far that has not come to pass. Instead, he has set himself an even tougher challenge: persuading investors that market-determined rates should come down. Specifically, Mr Trump and senior members of his administration want to bring down the yield on ten-year Treasury bonds. On February 25th it fell to its lowest level since mid-December (see chart). All going to plan? Not quite.