The US economy under Donald Trump is difficult to read. On one hand, the stock market is surging. Business investment is also on the up.But growth has slowed and the jobs market remains weak. Persistently high prices are also weighing heavily on consumers, a trend that is expected to rebound badly on Trump in the forthcoming midterm elections.The bond markets, the ultimate sanctioners, are also taking an increasingly dim view of Trump’s spending policies, which threaten to lob another $3.8 trillion (€3.3 trillion) on to the country’s $36 trillion debt.Proof of this came on Thursday night when the interest rate attached to 30-year US government bonds jumped to the highest level in 25 years.The sale of $25 billion long-term notes incurred a yield, or interest rate, of 5.216 per cent, the most since 2001.The high premium attached to US debt suggests investors are worried that inflation will remain high for an extended period, meaning the US Fed will keep interest rates high for some time.The relatively high borrowing costs will worry US Treasury officials as they need to fund the growing deficit.“Investors are being asked to absorb a growing supply of government debt globally at a time when deficits remain large, inflation uncertainty persists,” Michal Stanczyk, portfolio manager at Allspring Global Investments, said.“If investors continue demanding greater compensation for inflation and fiscal risks, long-term yields could move higher and away from 5 per cent even if Treasury auctions remain well covered.” Liberals say Trump inherited a strong economy and has spent 18 months tearing it apart. His tariffs have been inflationary. So has his ill-judged Iran policy. These dynamics have still to fully play out. But his controversial trade and tariff policies haven’t exactly tanked the economy: it is still growing and unemployment is still under 5 per cent. But investor concern is mounting.