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. Instead, the president has set himself an even more difficult challenge: persuading investors that market-determined rates should come down. Specifically, Mr Trump and senior members of his administration would like to bring down the yield on ten-year Treasury bonds. On February 26th it fell to its lowest level since early December (see chart). All going to plan? Not quite.