If the past three years have taught us anything, it is that low inflation cannot be taken for granted. Even though US inflation remains above the Federal Reserve’s 2% target for price stability, former president Donald Trump’s advisers are discussing a new and dangerous approach to monetary policy. If implemented during a second Trump presidency, it would undo the decades of hard work that allowed the Fed to reduce annualised inflation by nearly four percentage points since 2022, to roughly 3%, at little or no cost to the real economy.Trump’s advisers are reportedly considering two complementary policy changes. One proposal reportedly involves increasing direct presidential control over the Fed’s interest-rate decisions and rulemaking. Simultaneously, Trump’s trade team, led by former US Trade Representative Robert Lighthizer, apparently wants to weaken the dollar’s exchange rate.While some Trump advisers have denied any plans to devalue the dollar, Trump’s preference for lower interest rates and a weaker currency was evident during his first term. The proposed policies would make it easier for him to override the Fed’s independence and achieve both objectives. The result would be a potent inflationary cocktail.Trump’s desire for a weaker dollar is driven by his belief, shared by Lighthizer, that the dollar is “too strong.” This, in turn, makes US exports expensive in foreign markets and imports cheaper for American consumers, resulting in a large trade deficit. Both Trump and Lighthizer see this as problematic because, in the absence of balanced trade where imports equal exports in value, the United States is funding its trade deficit by borrowing from or effectively ceding domestic assets to foreign entities.But this interpretation reflects a myopic, 17th century understanding of trade and the economy. In reality, the inflows of money that sustain trade deficits can be used to build new factories, promote better use of existing US assets, or finance new domestic investments and enterprises, with positive spillovers to American workers and firms.To be sure, one could argue that a lower trade deficit boosts demand for US products, thereby creating jobs. But with the US already at full employment, the Fed is maintaining higher interest rates precisely to curb demand and bring inflation down. While the Fed was aided in that task by a stronger dollar, a weaker currency would have the opposite effect. Moreover, like the import tariffs favoured by Trump and Lighthizer, a weaker dollar would hurt consumers by driving up prices for goods containing imported components.Even if a weaker dollar and balanced trade were worthwhile goals, the policy options for achieving them range from infeasible to harmful. For example, the US Treasury and the Fed could purchase foreign-currency securities and sell dollar-denominated bonds. But given that the foreign-exchange market’s daily turnover is close to $8tn, these purchases would need to be implemented on a massive scale, which would expose the US government’s balance sheet to huge losses if the dollar were to strengthen.Currency-market intervention could be more effective if America’s allies supported it, as they supported the 1985 Plaza Accord. But while countries like Japan and Korea are becoming increasingly nervous about the weakness of their currencies, most others are not and would require convincing. And good luck organising a cooperative international effort while Trump is threatening to withdraw from Nato.US threats to impose tariffs on countries perceived to have weak currencies would introduce further uncertainty into global trade, potentially damaging investment and growth. Moreover, it is doubtful that any of this would significantly improve the US trade balance.Adjusting interest rates is a more reliable way to influence the dollar’s value. But given that foreign central banks are unlikely to raise interest rates and risk pushing their economies into recession just to accommodate Trump, the Fed would be under pressure to lower rates prematurely. This strategy would be inflationary and self-defeating, as higher domestic prices would offset any potential cost savings for foreign buyers that a weaker dollar might otherwise provide. Nevertheless, this might be the path of least resistance if Trump manages to establish greater presidential control over Fed policy, although it could just as easily worsen the US trade balance as improve it.A surefire way to weaken the dollar and reduce the US trade deficit is to shrink the federal government’s yawning fiscal deficit, enabling the Fed to lower interest rates sooner while controlling inflation. Although this policy would yield long-term benefits for the US and the global economy, it has virtually no political support from either Democrats or Republicans, including Trump.As global inflation spiked following the Covid-19 pandemic, some observers feared a return to the 1970s, when high and persistent inflation made economic life more unpredictable and stressful for households and businesses. Back then, it took a deep international recession to restore price stability. This time, however, inflation fell rapidly without the need for deep recessions, as supply-chain pressures eased and the Fed, along with other central banks, acted decisively to restrain demand by hiking interest rates.Central to this success was the fact that markets’ longer-term inflation expectations remained anchored. The actions of central banks, together with their consistent track records over several decades and institutional independence, fostered confidence that their efforts to tame inflation would be effective.These positive developments would have been impossible in a world where monetary policy was politicised, under presidential control, and focused on the dollar’s external value rather than its far more crucial internal value. Trump’s plans for the Fed and the dollar are a one-way ticket back to the inflationary chaos of the 1970s. — Project SyndicateMaurice Obstfeld, a former chief economist of the International Monetary Fund, is Senior Fellow at the Peterson Institute for International Economics and Professor of Economics Emeritus at the University of California, Berkeley.