The thing about trade, and the economics of trade, is that it is simultaneously desperately boring and desperately important.

For example, consider a little bit of legal small print no one spent all that much time thinking about until recently – a clause in most countries’ customs arrangements known as “de minimis”.

The idea behind de minimis is quite simple.

Collecting customs can be an expensive business. You need to employ lots of people to check goods, police the system and collect the relevant customs and tariffs.

In theory, you could fund that via the customs you’re charging people to import goods into the country.

But what if the items you’re imposing tariffs and charges on are so cheap that it makes no economic sense to actually impose those charges?

Consider a £5 t-shirt of the kind you might order from an online retailer such as Shein. In theory, that garment should face a 20% tariff when it arrives from China into the UK.

But since 20% of a small number is an even smaller number, most customs authorities, including those in the UK, have taken the stance of essentially excluding any cheap imports from paying customs. This is the ‘de minimis’ rule.

There are similar rules in most countries, with the main difference being the threshold at which they kick in. Here in Britain, de minimis applies to anything worth less than £135. In the US the threshold at which you start paying customs charges is higher: $800.

Now, there’s a long and detailed set of discussions that have bored on for decades about the pros and cons of this scheme. The historic arguments against collecting those fees were that a) doing so probably cost more money than it would raise, b) scanning and checking every import would jam up ports and airports unnecessarily and c) it might have a bearing on the wider economy as it throws further sand in the wheels of commerce.

But in recent years, a host of mostly Chinese retailers have exploited the de minimis rule to ship (actually, mostly to fly) cheap products to the US, UK, Europe and beyond.

The most visible of these companies are Shein and Temu. By directly flying consignments of very cheap clothes and consumer goods to airports in the west, they have been able to undercut other companies without having to pay customs fees.

All of which is why, alongside the host of other tariffs imposed in recent weeks, Donald Trump is also doing something else – eliminating America’s de minimis rules altogether. At least, that’s the plan.

Having pledged to do so in February, the administration rapidly reversed the decision after consignments began to pile up at US airports.

However, the impending rule, which is due to kick in this Friday, sounds like it might be more concrete than the last one. And, if it’s actually imposed, tariffs of 145% will be imposed on goods that, once upon a time, didn’t face any tariffs at all. Which is a very big deal indeed.

Already, prices on websites including Shein have begun to increase. Consumers have begun to abandon the sites’ apps. And consignments of goods bound for the US from China have begun to slow.

The real question is what happens next.

Does the White House U-turn again? Or does it stand firm? Even as American consumers see the cost of their hitherto cheap goods rise, and potentially even face empty supermarket shelves, the notion of which was summoned up by a delegation of retail chiefs who met with the president last week.

The short answer, as with so much about the current US administration is: no one really knows, and if they say they do, don’t believe them.

Lower stamp duty thresholds introduced at the start of the month are being widely blamed for the biggest monthly decline in UK house price growth since August 2023, according to a major lender’s measure.

Nationwide’s latest report on the housing market showed a 0.6% decline in April, taking the rolling annual rate of growth down to 3.4% from the 3.9% determined in March.

The bigger than expected decline has been widely explained by a slowdown in activity prompted by the stamp duty changes, which affected buyers in England and Northern Ireland at the beginning of the month.

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They had the greatest effect in England, where the changes included first-time buyers paying stamp duty on property costing £300,000 – up from £450,000 – while the surcharge for second homes also increased, by two percentage points, to 5%.

There was a rush to complete sales in March ahead of the deadline, which is also likely to have influenced prices.

But Nationwide said that April marked the first decline, in its measure, since August last year.

The lender’s chief economist, Robert Gardner, said: “The softening in house price growth was to be expected, given the changes to stamp duty at the start of the month. Early indications suggest there was a significant jump in transactions in March, with buyers bringing forward their purchases to avoid additional tax obligations.

“The market is likely to remain a little soft in the coming months, following the pattern typically observed following the end of stamp duty holidays. Nevertheless, activity is likely to pick up steadily as summer progresses, despite wider economic uncertainties in the global economy, since underlying conditions for potential home buyers in the UK remain supportive.”

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He pointed to the pace of wage growth continuing to outstrip inflation, coupled with low unemployment and retreating mortgage rates.

Rising expectations for a Bank of England interest rate cut next week, with a growing potential for more in the months ahead, are also forecast to bolster activity.

Prices have historically been supported by weak availability but estate agents have reported growth in seller listings as spring has got under way.

Donald Trump has celebrated the 100th day of his second term with a campaign-style rally in Michigan.

During his 90-minute speech the US president mocked Joe Biden, falsely claimed he won the 2020 presidential election and defended his decision to impose tariffs on countries around the world.

Speaking in front of electronic screens reading “100 days of greatness”, Mr Trump attacked “radical left lunatics”, briefly took on a heckler and boasted about his administration’s “mass deportation” efforts.

“Removing the invaders is not just a campaign pledge,” he said. “It’s my solemn duty as commander-in-chief. I have an obligation to save our country.”

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He played a video of migrants his administration claims are gang members arriving at a notorious prison in El Salvador, with those in the crowd cheering the images of deportees having their heads shaved.

During his speech, during which he called up several of his top team to the stage, Mr Trump claimed his administration has delivered “most profound change in Washington in nearly 100 years”.

Mr Trump also briefly touched on tariffs, saying China, which is facing tariffs of 145%, “has taken more jobs from us than any country has ever taken from another country”.

But he said his tariffs did not mean Beijing and Washington cannot “get along” and said he thought a trade deal with China was near, adding: “But it’s going to be a fair deal.”

“I think it’s going to work out,” he says. “They want to make a deal. We’re going to make a deal. But it’s going to be a fair deal.”

He claimed his administration had “already ended inflation”, but last month the Bureau of Labor Statistics said while inflation slowed in March over the past year, it had in fact risen 2.4%.

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‘You haven’t seen anything yet’

Mr Trump, who has frequently criticised Federal Reserve chair Jay Powell in recent weeks, said: “Interest rates came down, despite the fact that I have a Fed person who’s not really doing a good job, but I won’t say that. I want to be very nice. I want to be very nice and respectful to the Fed.

“You’re not supposed to criticise the Fed. You’re supposed to let him do his own thing. But I know much more than he does about interest rates, believe me.”

Mr Trump also defended his administration’s steep tariffs on cars and car parts, hours after he signed an executive order aimed at easing the impact of his tariffs on US carmakers.

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“We’re here tonight in the heartland of our nation to celebrate the most successful first 100 days of any administration in the history of our country,” Mr Trump said.

He later added: “We’ve just gotten started. You haven’t even seen anything yet.”