Boom! The US economy grew 4.1% in the second quarter of this year, the fastest pace of growth since late 2014. In the first quarter of 2018 growth was 2.2%, a bit stronger than initially estimated by the US commerce department.

This means that, a year and a half into his term, Donald Trump got the 4% growth he promised his supporters.

“GREAT” GDP numbers they are—on the face of it, at least. Dig a little into the broader data, though, and there are signs that the US economy’s pace of growth may be short-lived.

First off, let’s look at the trend. The way the government presents the data—annualizing growth since the previous quarter—can be pretty noisy. The good news is, the much smoother year-over-year growth in real GDP also suggests that momentum keeps trucking along.

On another positive note, the robust rise in that crucial engine of the US economy, household consumption, after a worryingly shabby showing in the first quarter of 2018.

Another measure of underlying demand—final sales to private domestic purchasers, which excludes trade, inventories, and government outlays—grew at a rate of 4.3%, the second-fastest since 2014.

But there’s reason to think the forces driving last quarter’s expansion lack staying power. A good chunk of the headline growth in the second quarter was boosted by a confluence of one-off and short-term measures by the US president.

Take trade, for example. Net exports contributed a whopping 1 percentage point to real GDP growth last quarter—the most since 2013. But there’s fair reason to suspect that this isn’t due to an out-of-the-blue resurgence of US manufacturing, particularly given that the dollar was fairly strong versus other major currencies during the quarter. Much of this could instead be a knock-on effect of Trump’s trade war, as importers snapped up US goods before looming tariffs drove up prices. For example, soybean exports have jumped as buyers tried to get out ahead of the retaliatory tariffs on the agriculture product by China.

But it’s unclear how the trade war will hit the economy in coming quarters. Companies are already reporting adverse impacts on business. GM, for example, said that higher commodity costs, from the tariffs on steel and aluminum, were eating into its profits and so cut its earnings outlook for the year, which wiped off billions in its stock market value. Harley-Davidson said it expects to take a financial hit of up to $100 million on an annual basis because of the tariffs, and so will move the production for EU bikes to international plants to try and mitigate this cost. In addition, it’s too early to tell whether trade war fears have crimped investment plans, which could deal a sharp blow to US growth.

Similarly, Trump’s signature tax cuts may have helped spur the 7.3% increase in investment in offices, malls, hospitals, and other nonresidential structures. Government spending also made a significant contribution following from a big increase in the budget approved by Trump.

Then again, overall investment fell versus Q1—meaning it dragged down last quarter’s real GDP growth. Growth in equipment investment was feeble, suggesting that tax cuts haven’t yet brought forth a US manufacturing revival. More ominously, residential investment—another big engine of US growth—fell by 1.1 percentage points, extending a slump in housing spending that began in Q2 2016.

When good news is bad

Today’s data also show that the US economy surpassed $20 trillion in nominal dollars in the first quarter. This is a long expansion—already the second-longest on record. In a year, it’ll overtake the decade-long period of consistent economic growth in the 1990s.

Signs are mounting that the US could be approaching the end of this economic cycle.

The end of the cycle is now the talk of the town. Analysts and finance execs have mentioned the “credit cycle” during earnings calls more than at any time since the last downturn, according to Sentieo.

Other signs that this expansion could be nearer its end? Job growth is well into its longest and strongest stretch on record, while the unemployment rate is at lows not seen since 2000.

Then there’s monetary policy to think about. The Federal Reserve is still raising interest rates, but the US yield curve is getting flatter. While that doesn’t have to mean a recession is imminent (the signal it’s sent previously), it does suggest that traders don’t think the US economy will warrant higher rates into the future—that there won’t be enough economic growth to support aggressive borrowing.

Meanwhile, the current stock market boom is less than a month away from overtaking the longest bull run ever, which ended when the tech bubble burst in 2000.

What lies beneath

Amid all this shiny numbers about national economic growth and job creation and stock market records, there’s evidence of more fundamental problems underlying America’s economy. GDP merely measures economic output, not well-being. It gives us only a partial reading on the health of the US economy because it tells us little about which Americans are benefiting from booming output, and how much.

US businesses have long since rebuilt their balance sheets; for most of the last decade, they’ve raked in handsome profit. Yet workers’ pay has barely grown, despite unemployment dropping far beyond expectations.

This staggering fact is more baffling still given Trump’s massive tax cut. In passing the measure, he and other Republican leaders told American workers to expect raises, promising that slashing tax payments of rich people and corporations would put more money in their pockets.

How’s that worked out?

As you can see, not well. Last month, average real pay actually shrank. That might be a monthly blip. Then again, it’s in keeping with an overall trend of slipping wage growth. Trump’s GDP paints a picture of a booming America. But the one most Americans live in is a bust.